Why I chose AD&D 2e

 In running 1e I ran into a consistent set of problems in my games that I just wanted to remove. The Half-Orc race, the Assassin and Monk classes, the wild power level of the Paladin, and Psionics. There was a lot I liked about 1e, too, such as the existence of Paladins, Rangers, Druids, and Bards, the really technical nature of stats, it’s reckoning of time and combat, and the attention given to equipment and weapons. I was considering cutting and splicing it all together into my own shitbrew, but then I found a game that does just all of that already; and that is AD&D 2e.

2e is not perfect - it’s reckoning of the combat round and weapon speed factor is inferior to 1e, it jettisoned the weapon vs AC table in favor of a much simpler damage type chart, replaced the table of repeating 20’s with THAC0, made character creation for Magic-Users, Clerics and Thieves more complicated by essentially adding subclasses, and incorporated the infamous non-weapon proficiencies.

For NWPs, I straight up will not use them, as I hate skill systems in D&D’s rigid class based game. The M-U (now called Wizards) spell school choice and the Cleric sphere choice is not something I personally like but players like having more options and it adds a bit of flavor to the classes. The Thief class benefits greatly from the points system. It’s going to be very hard to let go of 1e’s extremely technical combat, so I probably won’t.  Other than that, everything else from 2e flows seamlessly from 1e, so I don’t anticipate any conversion issues.

I envision my 2e game as playing very differently from my 0e one. My OD&D game is all about free form actions and occasionally instant death, where every action is adjudicated by out-of-game logic, while my AD&D 2e game will be beholden to the dice mechanics and graven rules.

The Monstrous Compendium is actually really neat, too.

Supplement I: Greyhawk -review

I finally sat down and read this book. I've previously discussed OD&D, but I've restricted myself to just the 3 LBBs. I liked the material contained within them but I found it limiting, both in terms of the expansiveness of the game and in terms of prepackaged content. Greyhawk adds more content and tries to add more concrete rules to the game and smooth over some incongruities.  This is really the supplement that adds more 'crunch' to the game.

  Within this supplement, the game begins to take on the shape that is recognizable as AD&D and the Basic boxed set line - variable HD for classes, variable weapon damage, all stats now give conditional bonuses for high scores, etc. The infamous strength table and the percentile strength makes its appearance here, though the bonuses it grants are much less than what makes it into AD&D.

 The Thief and Paladin classes are also introduced, but again much weaker than what they will eventually become. The Thief exists as a set of useful dungeoneering skills, and allows Dwarves and Hobbits a second class they can opt for. Multiclassing is also introduced for demihumans, thus cementing the separation of race and class  in the D&D game. The Paladin, as presented in Greyhawk, is just a lawful good fighter that has a limited ability to heal or cure disease, and at higher levels gains extra powers with his holy sword and steed. This version of the Paladin is much less powerful than his AD&D counterpart, who can also cast spells and has a constant aura of protection from evil.

The weapon vs armor to-hit bonus chart appears in Greyhawk, but it has a lot less entries than the one in AD&D. It is clearly a holdover from Chainmail, but given how many publications it has appeared in, I strongly suspect that circa 1977 Gygax used weapon vs armor bonuses in his game. There is more discussion of using the alternate combat system to play D&D, further reducing the need to have a copy of Chainmail to play.

Like every one of Gygax's rulebooks this is poorly laid out and poorly worded, but personally I've spent enough time reading old school D&D rules to be able to pick out the important highlights. Adding the 3 LBBs and Greyhawk together gives a game very similar to AD&D but much more restrained in power and scope. The bonuses for PCs and monsters are smaller, and all classes don't get the fantastic tools that they would get in AD&D. Personally, I would prefer to play this game over AD&D, as I feel that the number crunch of AD&D is much worse, while everything else is otherwise the same.

Ranting against “A Quick Primer for Old School Gaming”

    I do not like this PDF (I’m not going to link it because you require an account or some junk to download it, and I don’t recommend it anyway). It intends to show the difference in gameplay styles between old D&D and modern, but it does so terribly, by creating a straw man DM as an example of modern gaming versus an example of a “true” old school DM. And in the end, the old school DM and the modern DM end up doing the exact same thing.

    In one of his examples, the PCs come to a room trap. The modern DM has them roll an ability skill check, while the old school DM has them talk out the solution (“roleplaying”). This is the crux of the difference, according to the Primer - player skill over character skill, rulings over rules. But nothing, literally nothing is stopping the modern example PCs from just talking out the solution, and their DM going with it. This is a bad example, and unfortunately every example is like this.

    And in the end, the result is the same, a minor trap, which players overcome with some natural ability.  The modern DM actually has more options in that example than the old school DM, as he could encourage role play and sprinkle in some skill checks as desired.

    Full disclosure, I do not use skill checks in my games, but I’m consciously reacting away from modern D&D design which is heavily reliant on them.

    While I like the sound of “Player skill over character skill”, I think that example misses the point. Instead, what I would highlight is that players cannot use die rolls and skill checks circumvent or get out of difficult situations in the game! A natural 20 means nothing in old school D&D and that’s something I generally have to train modern players out of expecting. Old school D&D is meant to be a simulation of a living world, not a balanced set of mechanics. When players encounter a hazard, or trap, or unknowable situation, they must engage with the simulation and attempt to deconstruct it and overcome it. That’s what the Primer narrowly defines as “player skill”.  Instead of “Player skill over character skill”, I would substitute “Simulation over mechanics”.

    The second issue I have with this PDF is the notion of “Rulings over rules”. Because the original D&D rules were very sparse, and more like a collection of Dave Arneson’s and Gary Gygax’s notes, all other groups had to invent circumstantial rules in actual play. The PDF codifies this style of off-the-cuff rulings as a hallmark of old school gaming. I disagree. One only has to look to AD&D to see that codifying the rules of the game was a very early impulse, once the folks at TSR saw how the game began to be played “out in the wild”.

    In fact, I believe that in either OD&D or AD&D, it is specifically mentioned that the referee should keep a notebook of all such off the cuff rulings made during the game session, and refer back to them for consistency. In effect, every GM would be codifying his or her own rules. Players like consistency, and a GM who makes two different rulings on similar situations would quickly be called out on it.  Instead of “Rulings over rules”, I would once again substitute “Simulation over rules”.

    And that’s actually what I like about old school D&D, in that it is about crafting a consistent, logical, and believable world that the players have to engage with directly and use their imagination to navigate, rather than with their character sheet and using dice to “win”.

    And the real difference I believe between old school and modern D&D is this: In early D&D, the DM was the driving force behind the game, who set up the verisimilitude of the world and arbitrated the player’s actions within it. In modern D&D, the players are the drivers of the game, using their ability scores and dice rolls to overcome numerical challenges that the DM can only set the difficulty threshold to.  From 3e onward, limiting the DM’s influence over the players was a stated design goal. And that, more than anything, changed the nature of the game.

Original D&D (Single Volume Edition) by Greyharp Review

The DM of a group I was playing in wanted to switch over to Original Dungeons and Dragons, and shared this PDF of the 3LBBs compiled into one volume. This volume is mostly just a reorganization and mild editing of the original 3 volumes, but the results are astounding. Presented in this manner, the OD&D rules are clear, concise, and as simple and complete as E. Gary Gygax always claimed they were. In fact I'd go so far as to say that this version of the rules is flatly superior to AD&D.

The opening foreward of the book is written by the compiler, and he addresses the criticisms that I have had about OD&D: That they are incomplete, poorly presented, and more of a toolkit for the referee to flesh out than a full game in themselves. He disagrees strongly, and to prove his point presents the rules in a manner that does make them a complete game. I've read the original 3 LBBs deeply and can find no great inconsistencies with this volume, so I would have to say that he has succeeded by far.

Here's the thing, though. To understand OD&D you need a strong foundation in some other edition of TSR D&D - whether its AD&D, B/X, BECMI, or the Holmes Basic book. This PDF is written with such an audience in mind, one that is very familiar with classic D&D and has been playing it for some time.  OD&D is not a game for beginners or newbies to tabletop role playing games.

While actually playing the game, however, I found it mechanically indistinguishable from the BECMI games I'm fond of. In fact, while playing, I was missing some of the options from a fully featured BECMI game. It felt like I was playing the same exact game, just with less stuff.

In fact I had done an experiment myself a while back, where I considered just throwing out all later rulesets and running a game of OD&D by itself. To that end I printed out the reference tables, and was in the process of putting together a game session. What I noticed was that all the material on the OD&D tables was identical to BECMI, there was just less content - less monsters, less magic items, and an entire class was missing.

However, this compilation of OD&D has also changed how I view the B/X and BECMI rules. Instead of a separate game, I now see the BECMI boxes as intro sets to OD&D, the first literally being the beginner's set from levels 1-3. 

Mythic Game Master Emulator Review

The Mythic Game Master Emulator provides three powerful tools that allow you to play tabletop roleplaying games without a GM: The Fate Chart, the Random Event tables, and the Adventure Sheet.

The Fate Chart is the core of the Mythic GME system and provides the basic foundation for play. It is a complicated yes/no system, a so-called "oracle", that is meant to handle any random question with an unexpected result that would normally be asked of a DM. The Fate chart provides the entirety of Mythic's task resolution system, and the outcome of every action should be posed as a yes/no question to be rolled for on the chart.  The Fate chart also acts as the main content generator for the system, and it is implied that worldbuilding tasks such as setting up the features of a setting, NPC encounters, and social situations can all be handled through it, though there is an admonishment in the book not to go overboard with dice rolls but use logic instead.

The Random Event Focus and Event Meaning tables are the only concrete tables in the book. They present a list of items that, when combined, must be interpreted to create a new event occurance in your game. The GME says to use these tables only on a double number dice roll, but they're also useful at any point  when you're unsure of what to do next in game. The Event Meaning tables are essentially just tools for guided inspiration in story telling, much the same as Rory's Story Cubes, or a Tarot Deck, or any other such tool that invites creative interpretation. The Event Focus chart is meant to give the Event Meanings a concrete effect in your game.

The Adventure Sheet is the framing device that holds the rest of the game together. Every game session, or every adventure, is meant to be a collection of scenes in which a dramatic conflict is posed and resolved. The worksheet itself contains entries for scene setups and resolutions, as well as places to list NPC actors and story threads. The story threads are also a unique idea that provide guidance to the flow and purpose of the game, as well as adding another element of unpredictability.

I found the Mythic RPG to be more useful as a creative writing tool rather than a fun game to play solo. In fact, when it comes to specifically playing solo, I found the experience of using the Mythic RPG to be more akin to doing English Literature homework with dice or doing my taxes instead of actually playing a game.

The greatest weakness of the Mythic RPG is that it tries to be completely generic. I understand that the goal is to allow the players to fit it into whatever setting or type of story they want, but as a result it loses concrete mechanics to actually support an individual fantasy. In fact, for any type of game you want to play, it is better to use a system with concrete mechanics and only use the Mythic GME to fill in the missing "gaps".

Its clear that the main appeal of the Mythic system is the GM Emulator. The instincts of the author were correct in first creating an RPG to show off the Emulation system, but then separating the Emulator out to be its own standalone system. The Mythic system is too abstract and generic to support actual play, unless layered on top of another RPG system.





The traditional role of a Game Master is to describe the environment to the players, and to narrate the results of their actions. Or, to restate in technical jargon, the GM provides content generation and action resolution.

The sea-change, breakthrough moment of the Mythic GME is in using the Fate chart for action resolution. Every action can be posed as a yes/no question and rolled for a result on the Fate chart. Every scene should begin with a question describing the dramatic conflict ("how do my player characters overcome this immediate challenge") and a series of answers rolled on the Fate chart can provide the resolution ("are they successful"). Once you separate the distinct tasks of content generation and action resolution from one another, the use of the Fate chart, Adventure Sheet and Event tables become more clear.

But the book itself does not do this. Instead, it confuses the issue by using the Fate chart for content generation and action resolution, and then admonishing the player not to go overboard with content focused questions.  A better solution would be to use the many random charts, terrain, events, and encounters that can be found in an RPG such as D&D or on online blogs for content generation.

The D&D Dungeon Master's Guide has appendices devoted to random generation of terrain, dungeon layout, wandering monster encounters, and even random generation of NPC personalities. The 5th Edition DMG also provides a chapter on random generation of quests, story, and plot twists, which can be used to buffer the Scene Setups worksheet.  D&D also provides a robust action resolution system, such as the d20 system.

OSR players are generally comfortable creating an entire world through random tables, and are happy to simply wander about this world in search of treasure and to fight monsters, but need a GM to supply concrete action resolution as the rules can be conflicting or incomplete and OSR gameplay stresses creative thinking and unpredictability in action. For this, the Fate chart is the most useful.

Modern D&D and 5e players have a universal system for action resolution and just need to provide an appropriate CR to modify their chance of success, and the thresholds are helpfully given in layman's English to make this determination easier, but they are generally floundering when it comes to a purpose for their game, as they are trained to seek "plot" and "narrative" as reasons to play. For them, the Adventure Sheet and the Event tables are the most useful.

In my own games, I found the Mythic GME of limited use. I could create a game world straight out of the random tables in the Dungeon Master's Guide and adventure through it, and I could use all the rest of that game's mechanics to resolve my successes. I only needed the Mythic GME to fill in the gaps of certain elements that weren't immediately obvious.  The Mythic system might have changed the way we see RPGs, and probably kicked off the whole solo RPG community, and its definitely worth the read to understand how, at a fundamental level, the tasks of a GM work and how they can be represented mechanically through dice rolls.

However, I will complain that this book is presented backwards. It shows you its most important mechanic first, the Fate Chart, followed by everything that's connected to it. This leaves you to puzzle out for yourself how to actually use all its mechanics. Instead, it should have presented the Adventure Sheet first, as its the first thing that you'd pull out for your game session, and explained it first before moving through the Randomness chapter, Event Tables and then Fate Chart, as that's generally how you would use them during actual play.

OD&D vs B/X and BECMI

Again, what’s striking to me is how much is the same. I was initially under the impression that AD&D was a compilation of everything OD&D, while the “Basic” strain of D&D was a restructuring by different authors using the same underlying principles. But after cross referencing the source rule books a few times, I’ve come to the conclusion that that’s not the case at all. The rules and information in the Moldvay and Mentzer sets are very similar as what’s given in the three original D&D booklets, just vastly improved in clarity, organization and explanation.

Like the Moldvay set, OD&D basically runs on a d6 system, not just for weapon damage but for resolving success of most situations, such as finding hidden doors and avoiding traps. The d20 is only used for combat resolution on the alternate combat table. OD&D is notorious for how much of its game system is actually not detailed in its core books, and those gaps are filled in by the Basic and Expert sets.

It actually gives me more confidence in considering the whole line of "Classic" D&D rules to be one continuous strain beginning with OD&D and re-edited right up to its last revision with the Rules Cyclopedia.

The modern OSR attitude seems to be that OD&D and B/X/BECMI are two different strains of the game, but I believe that part of that might be driven by an urge for purism in rulesets and a highly elitist attitude among OSR gamers. During the '80s and '90s when these books were in print, there was no distinction between the flavors of Classic D&D since they were all branded as the same, and I think the OSR attitude is an overreaction to that which focuses on the most minor differences in wording and table values.  And this is understandable, since most OSR games owe their very existence to minor differences in wording and table values, and legally could not exist without them.

Coming back to D&D, the high degree of compatibility between the successive versions makes it much more useful to cross reference between them, and to use the information in one book to fill in the gaps of the other.

Moldvay vs Mentzer

What's striking to me is how much is the same between both. Even short, throwaway rule guidelines from the Moldvay book are carried faithfully forward by Mentzer into his revision. It's clear to me that Mentzer did not intend to change the rules much at all, merely re-edit and present them in a more expansive, instructional format. The few changes he did make are mostly to be more generous to players, for example encumbrance limits are raised. The big exception are the Thief skills, which were a casualty of marketing - they had to be stretched out to 36 levels, so their actual gain per level is slower, which makes the Thief more useless for longer.  The actual mechanics, however, such as movement, speed, combat, item prices, etc. are exactly the same.

Neither Basic set contains a method for random dungeon generation. Instead they contain guidelines on building a dungeon and how to stock it, but the actual layout and method is left up to the DM.  The Mentzer Basic book is actually the same as the earlier revision's, just expanded. This makes the AD&D random dungeon generation table (copied from an article from TSR magazine) unique.

The big pillars of the OSR community are the Moldvay, Cook and Marsh B/X sets, and Allston's Rule Cyclopedia. The BECMI sets sort of get lost between them, since they're assumed to be superseded by the Rules Cyclopedia. The value of B/X and Rule Cyclopedia is that they're both written as reference works, and thus much easier to look up during actual play, while the big flaw of the BECMI sets is that the rules are divided between Players' books and DM's books, and the rules, items, and magic lists are scattered between the 5 sets, making them tedious to look through during a campaign.

Fans of B/X prefer its "simplicity". Restricting itself to 14 levels (though it Cook's Expert hints at 36), the Basic and Expert sets cover dungeon crawling and overland adventures, which is the same focus as D&D's original Underworld and Wilderness Adventures, and to it's proponents that's all you need. It's hard to argue otherwise, since modern D&D doesn't do anything different.

The Rules Cyclopedia, on the other hand, combines everything from the development of the Basic/Classic line into one book. This means it pulls in optional material such as skills and demihuman classes from the Gazetteer books, the large scale combat and dominion rules from the Companion set, and the weapon mastery and immortal paths from the Master sets, and even some hints from AD&D 2e. It takes an "everything but the kitchen sink" approach to the rules and those who have it give it nothing but praise for combining everything about D&D you would ever need into one volume.

However, people who quibble about the rules differences between the editions are barking up the wrong tree.  The Rules Cyclopedia replaces some of the edits put in by Mentzer by carrying forward the original rules written by Moldvay, but then in other places uses the same text as Mentzer's BECMI set. The Classic D&D line does not have the major differences between editions that AD&D 1e and 2e, or D&D 3, 4, and 5e have had.

Underworld and Wilderness Adventures

The actual method of how to play D&D is contained in this volume. Men and Magic and Monsters and Treasure describe the things in D&D and how to use them, but the actual explanation of what to do in the game is written in Underworld & Wilderness Adventures.

And there's not a lot in there. The first section describes dungeons and how to build one followed by a brief discussion on how to explore it, with a couple of short asides on how to actually use some of the items detailed in the equipment list.* This is followed by a discussion of combat procedures in the dungeon, which explicitly directs readers to Chainmail for an in depth explanation, or they can use the very sparse charts from the alternate combat system in volume I.

The next section is Wilderness and it basically directs the reader to Outdoor Survival for the actual exploration rules and a map on which to play. A short discussion on converting the Outdoor Survival map for D&D play follows, and the rest of the book is taken up by combat procedures on land, aerial and naval.

What's striking is what's missing. There is no discussion of roleplaying, no mention of town adventures, of chats with NPCs, no instructions for the creation of a campaign or set up for heroic quests. D&D is primarily and explicitly only about combat, on a 1:1 figure scale in a fantasy setting either in the underworld or overworld, with monsters and heroes.  What people actually consider an RPG to be is completely absent.

Maybe all of that is contained in the supplements and Strategic Review magazine, but then that would mean that to canonically play D&D as an RPG requires a whole host of sources beyond the basic 3 booklet set.  Everything I've mentioned that was missing is actually in AD&D and the later Basic sets.

*which I found way more helpful than most other D&D source books since this information is not restated anywhere else until the Mentzer red book.

Best review

http://dungeonofsigns.blogspot.com/2015/12/lost-mines-of-phandelver-review.html

Best comparison of Holmes Basic, B/X, and BECMI that I have seen

From RPG site forums

USC professor, occasional novelist, and (apparently) D&D fan Dr. J. Eric Holmes, as legend has it, took the OD&D rules (including Supplement I: Greyhawk), his own understanding of how some of the more cryptic parts were supposed to work, and possibly some common house-rules (it appears he must've had at least second-hand knowledge of "The Perrin Conventions" -- a set of combat house-rules used at Bay Area con games from 1976 on and eventually published in vol. 2 of Chaosium's All the World's Monsters), and decided on spec to re-edit the whole thing into something that made better sense and was more comprehensible to beginners, and then approached TSR with his manuscript and said "want to publish this?"

As this occurred right around the time D&D was beginning to really take off in popularity, and while Gary was immersed in is own attempt to compile OD&D+supplements into a more comprehensive and comprehensible game (AD&D) they took him up on his offer. Gary Gygax "revised" Dr. Holmes' manuscript and made a few changes -- mostly inserting plugs for the upcoming AD&D game, but also inserting a few tidbits from the working drafts (a couple spells, a couple monsters) -- and TSR released it as the DUNGEONS & DRAGONS Basic Game Set in the summer of 1977, both as a stand-alone book and in a boxed set together with copies of TSR's already-released Dungeon Geomorphs Set 1 (a set of blank maps), Monster & Treasure Assortment Set 1 (tables of pre-rolled encounters & treasure-lists) (Judges Guild hadn't yet proven to TSR the potential popularity of pre-designed dungeons, i.e. modules), and a set of dice.

Unsurprisingly, given its genesis, this was a strange set -- it includes some (but not all) of the new rules content from Supplement I (thieves are included, but only for humans (whereas SuppI allowed all races to be thieves); the convoluted chance-to-know spells by Int stat table is included for magic-users, but not the combat bonuses by Str table for fighters; variable attacks and damage are included for monsters (e.g. ghouls having 3 attacks for 1-3 damage each) but not characters (so all weapons do 1-6 damage regardless of size), and so on), its advancement tables only cover levels 1-3 but there are numerous unexplained references to higher-level characters and spells and a lot of included monsters (giants, dragons, vampires, trolls, etc.) that are way-overpowered for level 3 characters (not to mention the tables in the Monster & Treasure Assortment which contained numerous monsters, level 4+ character-types, and magic items not described in the rulebook), and the combat rules (which were largely absent from OD&D -- each individual referee was expected to cobble something together from Chainmail and his own common sense) don't bear much similarity to any TSR edition of D&D before or since (including anomalies like that each combat round lasts 10 seconds but 10 combat rounds equal a 10-minute exploration turn, that initiative order is determined by Dexterity score (which requires assigning Dex scores to every monster encountered), the fact that (even though all weapons do 1-6 damage) daggers attack twice a round and two-handed weapons attack once every 2 rounds, and that flaming oil is WAY better than any other attack form (doing 3d8 damage across 2 rounds)).

However, despite all this, and even after the AD&D books were released and had significantly-enough different rules from OD&D to render all those references Gygax had inserted incompatible, this set was popular enough to be reprinted about a half-dozen times over the next 2 years (including "upgrades" to the boxed-set version to include full modules -- first B1: In Search of the Unknown, later B2: The Keep on the Borderlands -- instead of the geomorphs & tables, and a downgrade when TSR ran out of dice sets and started including a sheet of "chits" instead).

Finally, in 1980, TSR decided to finally take the old OD&D whitebox (which had been sold as a legacy product, the "Original Collector's Edition," since 1977) out of print and replace it with a new, mass-market-friendlier edition (rumor has it TSR's legal settlement with Dave Arneson, who received co-author credit and royalties on D&D products but not on AD&D products, was also a factor in this decision -- that they were required to keep the former in-print, and distinct from the latter, to keep him from suing). This ended up being two sets, the Basic Set (a new revision of the Holmes set by Tom Moldvay) and the companion Expert Set (filling in all the gaps from the OD&D rules that weren't included in Basic, edited by David Cook and Steve Marsh).

Tom Moldvay's Basic Set is clearly based on the Holmes set -- it includes all of the same classes (including human-only thieves), most of the same spells (including Gygax's added AD&D spells like Remove Fear and (Tenser's) Floating Disc), more-or-less the same monsters and magic items (including those drawn from Supplement I like rust monsters, stirges, carrion crawlers, and gelatinous cubes that had no basis in pre-D&D literature or mythology) -- but the rules are considerably cleaned up and streamlined, with a lot of the weird little anomalies eliminated or made to fit more logical patterns. For the first time with Moldvay's set, the D&D rules actually worked and made sense as-written, without requiring each individual to essentially co-author the game.

The Cook/Marsh Expert Set was a direct sequel/companion to Moldvay's set that was also usable with the Holmes set (including a page of conversion notes at the front covering the main differences between the two), covering levels 4-14 (not sure why that particular number was chosen -- perhaps because it looked aesthetically pleasing on the book cover, or because that's where the thief's abilities max out in Supplement I) and including all of the "missing content" from the OD&D set -- the expanded advancement tables, higher level spells, more (and tougher) monsters and magic items, and the rules for wilderness adventuring (which had been completely glossed-over in the Holmes set) and castle-building (the original "endgame" for D&D) -- all slightly tweaked to fit and be compatible with Moldvay's revision of the system. Interestingly, nothing from Supplement I -- neither spells, nor monsters, nor magic items -- is included in the Expert set unless it had already been included in Holmes and Moldvay. So the Expert Set doesn't include, for instance, the Monster Summoning spells (or any spells above 6th level), the tougher Greyhawk monsters like ogre magi, umber hulks, and beholders, or anything from Greyhawk's extensive magic item lists (except for those couple of items -- bag of devouring and rod of cancellation -- that Holmes, and therefore Moldvay, had included).

These sets were also on the market for about 2-3 years (from late 1980 to mid 1983) and proved even more popular than the Holmes set (these were the "D&D fad" years, with 1982 apparently being TSR's all-time high water mark) and it was eventually decided to make an ever more beginner and mass-market friendly version of the game, and simultaneously "complete" it with the level 15+ rules that had been hinted at in the Expert Set (as the "D&D Companion") but never released (or, from what I understand, written). This job fell to Frank Mentzer, who had already had success overseeing TSR's line of choose-your-own-adventure "Endless Quest" books.

Mentzer's Basic Set is ruleswise almost identical to Moldvay's (there are a couple small differences, but nothing a casual or even moderately-dedicated player would notice) but radically different presentation-wise. Moldvay's book is organized as a straight-forward reference book; Mentzer's is a step-by-step instruction manual, including a (presumably Endless Quest-inspired) choose-your-own-adventure intro that takes up the first 20 pages of the book and lets the reader "play" D&D before actually presenting any of the rules. The result is that the same amount of rules now fill up double the page-count, and are much easier for beginners and young players (the boxed recommends ages 10 & up, down from Holmes' "adults ages 12 & up"), but are less convenient for in-game reference and have an authorial voice and tone that comes off as mildly condescending.

Mentzer's Expert Set is really just a reorganization of the same content as the Cook/Marsh version to better match the organization and look of the new Basic Set, and with some of the progressions slowed down at the upper levels to allow more "room at the top" for the planned Companion & Master sets. In addition to slowing down characters' saving throw advancement, thieves' skills, and cleric & magic-user spell acquisitions, a couple of the more powerful spells, monsters, and magic items are also held back and (IIRC) the castle-building rules are less detailed. Instead, we get a detailed sample base-town, and a couple pages discussing in-town adventures (something that OD&D had covered very briefly in a couple paragraphs and Cook & Marsh had ignored completely).

The D&D Companion Set (released in 1984, a year after the revised Basic & Expert Sets) was also written by Frank Mentzer, and includes both more complex optional rules (new sub-classes, new weapons with special effects (like nets and bolas), rules for wrestling and jousting) and extensive rules for higher-level (15-25) characters, focusing mostly on the establishment and administration of Dominions. There were also a set of abstract mass-combat rules, and some new, tough monsters. In retrospect this is where the line between mass-market-friendly D&D and hobbyist-oriented AD&D began to blur -- with the former becoming in some ways more detailed and complex than the latter (which never had an equivalent "High Level Campaigns" book in this era, and pretty much petered out after about 18th level) -- and the two lines began to look less like alternate approaches to the same general game and more like two distinct, competing games.

In the Holmes era, it was explicitly spelled out that you were supposed to play with the Holmes set until you hit level 3 (which was envisioned as taking about a dozen up to maybe 20 sessions) and then you'd switch over to AD&D. The Moldvay-Cook-Marsh sets don't actually say that (possibly because they couldn't because of their settlement with Arneson), but this still seemed to be the way they were actually used in practice -- start out with the Basic Set, play it up to level 3, get an Expert Set and play it for awhile, but eventually "graduate" to AD&D. I know plenty of people who played up to about level 6 or 8 (i.e. about 6-9 months of play) in Expert D&D before switching gears to AD&D, but I didn't know of anyone at the time who actually stuck with it all the way up to 14th level (which would, at the assumed advancement rates, take at least a year of play, possibly more like 2-3).

Thus, the Companion Set seemed weird, like it was saying that you weren't supposed to switch over to AD&D and were instead supposed to stick with this game for a multi-year campaign (which was reinforced even further with the release of the Master Set (covering levels 26-36) in 1985, and the Immortals Set (essentially a whole new game for characters who have "won" Master Set D&D and become immortal) in 1986 -- to actually get to use either of these in play would require several years of dedicated, regular play, which was (as we had always thought) what AD&D was supposed to be about, not the mass-market kid-friendly version).

I'm convinced TSR simply never thought this through, never considered that they were setting these games up not to have the mutually-beneficial symbiotic relationship they'd had in the Holmes and Moldvay days (start with the simple set, spend a few weeks to a few months playing through it and learning the game, then move on to the Advanced game which you can (at least theoretically) continue playing for years) but to be in competition against each other -- that by encouraging players to stick with D&D through the Companion, Master, and Immortal levels they were no longer adding to but taking away from sales of their flagship game.

But then, considering that this was the same era when TSR began introducing multiple different AD&D campaign settings and marketing each one as, essentially, a separate game -- that Dark Sun and Ravenloft and Dragonlance and the Forgotten Realms (and, ultimately, more than a half-dozen others) didn't really overlap and characters or adventures intended for one couldn't really be used in the others, meaning that casual fans would pick one favorite setting and ignore product branded for use with any of the others, thus hopelessly fragmenting the customer base and ensuring that nothing would achieve the kinds of sales levels that "universal" products and adventures saw back in the early 80s -- I suppose I shouldn't be too surprised...

(tl;dr version: the OD&D, Holmes, Moldvay, and Mentzer sets are all pretty close to the same, especially if you compare A to B, B to C, and C to D instead of A to D; TSR made a dumb mistake from 1984 on by ceasing to use the D&D line as a de-facto introduction to AD&D and instead trying to make it into a complete stand-alone (and thus competing against rather than feeding into AD&D) game)

An Actual Review of B/X and BECMI D&D

They're the same. The BE of BECMI is identical to B/X, intentionally so, as some passages are lifted word-for-word. There are a few minor changes - BECMI smoothens out the Cleric and Magic-Users' spell progressions, and stretches out the Thieves' Skill progression over 36 levels. The Thief skill progression is the only flaw, as it lowers the class's chance of success per level, but there are many solutions to this problem online, not the least of which is simply to go back to the old progression system.

 Mentzer Basic and Expert were also written as tutorials for absolute novices who may have never even heard of role playing games before. This was intentional, as the BECMI sets were TSR's forays into the international market. As such, Mentzer Basic includes a solo tutorial adventure and a group tutorial dungeon spread out over two books, instead of Moldvay Basic which only has a sample dungeon and a short example of play. For modern, experienced gamers, the tutorials are considered unnecessary. 

 The 1981 Basic set came with both Moldvay's Basic rulebook and an adventure, B2 Keep on the Borderlands. This clear separation of rules and adventure made referencing the rules much easier. The 1983 set came with a Player's Book and DM book, both which had tutorials and rules split between them, which made them more difficult to reference.

The BECMI Expert book contains additional content over B/X Expert in the section for Dungeon Masters. B/X presents a map of Karameikos and the Known World as a sample wilderness, BECMI presents a sample town called "Threshold" with a light amount of detail, and some quest hooks around it.

What BECMI adds over B/X is extra content for higher levels, the CMI books. The Companion book, in particular, adds rules for stronghold construction, management, and mass warfare; making it unique. To get a similar situation in OD&D you would have to incorporate the Chainmail Mass Combat rules, which were originally meant as a tabletop miniatures wargame anyway, or AD&D 2e's Battlesystem, which is an awful approximation of it. The Companion set's stronghold rules also let you play out a small Sims-like domain management game, if you'd like.

The Master and Immortal sets add in high level artifacts, weapon specializations, the quests for Immortality, and the whole new Immortals system of combat and magic. Most players and groups are obsessed with dungeon crawling and fighting larger enemies, and throw out the late game content of BECMI, and I think that's a shame, because the value I see in the Master and Immortal sets is that they provide new and unique gameplay additions that keep the game from going stale. Modern D&D has no such content, and simply adds more powers and more class features for players to attain as they gain increasing numbers of levels, and I really think that limits the scope of the game.

B/X is generally praised for the conciseness of its text and its ability to convey all the information of the game with the brevity of its language. BECMI uses longer form explanations and more advice and guidance on how to play the game. For this reason there is an impression that the Mentzer books talk down to the reader, while the Moldvay, Cook and Marsh books use more adult language. Personally, I've never had an issue with it. I'm still struggling to figure out what the hell Gary Gygax is trying to convey in the OD&D and AD&D books.

A complaint I've seen online is that it is hard to find rules in Mentzer BE due to its tutorial nature. While the rules of the game are introduced slowly in the tutorial, they are all collected and presented as a reference at the end of the book. The organization and wording is identical to Moldvay Basic, as I've mentioned before, so I don't understand this complaint. The Marsh and Cook Expert book, in particular, has terrible organization and the Mentzer Expert book doesn't change any of it, but just uses more words in the descriptions.

The appeal of B/X is in the brevity of the text and the limited scope of the gameplay that covers only what OD&D did, with its focus on Underworld and Wilderness Adventures. With the OS Essentials book out, which takes the content of the B/X levels and reorganizes them into something better referenced for play, its become the dominant game books for OSR type D&D.

The BECMI books go far beyond, delivering on the promises of OD&D by including domain level play, more integration with the Known World campaign setting, and rules for deity-tier Immortals play that doesn't devolve into killing Odin for his magic spear.

As an aside, some people prefer the amateurish art of the B/X books, as they feel it more accurately represents the gritty, high risk dungeon crawling style of early D&D play, and dislike the more professional, high fantasy art of the BECMI sets.

In the end it comes down to personal preference. Some players prefer to reference B/X as a slim set of volumes to keep on hand for game sessions, while others prefer the longer form tutorials and explanations of BECMI as a way to learn the game. Mechanically, there is no real difference, in fact you can see BECMI as merely as an incorporation of errata and an update to the B/X rules.

A point worth mentioning, and something really negative about BECMI was the politics surrounding its creation. As part of the ongoing lawsuit between Dave Arneson and Gary Gygax, TSR attempted to remove everything copyrightable from D&D and keep it in AD&D, which is why a lot of the special races like Drow don't appear, and the names of magic spells such as "Tenser's Floating Disk" were renamed to just "Floating Disk".  Frank Mentzer seems like he didn't want to be caught in the middle, and credited both the creators of D&D in his publications. The BECMI sets were also created to be TSR's international products, which explains the shift in tone and language of the rulebooks.

B/X and BECMI are so similar, and they're in continuity with Original D&D "0 edition" in a way that the two editions of AD&D are not, that the choice of which to play and purchase really is a matter of personal preference. Most old school fans of D&D tend to stick with whichever they got first.

OD&D is not a complete game

I made this comment on one of my videos and got called out for it by a fan of the original edition of Dungeons and Dragons. According to him, there's a large fanbase that still plays and enjoys the original game and that I could gain more insight on it by seeing what they do. Fair enough, and I dove into looking at the original brown box set and the released supplements.

As a caveat, I haven't played a session of OD&D so I'm limited to reading the books and looking up what the fans have to say about it, but I stand by my earlier assessment. The original 3 books of Dungeons and Dragons were never meant to be a stand alone game. They're a product of the war game culture of the 1960's and 1970's, where the players took many different sources from many different systems and blended them into their own campaigns. The first 3 booklets of D&D were introduced into this culture with the expectation that they would be added as one part of the players' ongoing campaign. The books themselves explicitly assume use of the combat rules from the game Chainmail: Rules for Medieval Miniatures and the wilderness journey rules from Avalon Hill's game Outdoor Survival.

The original release of D&D is a skeleton of a game meant to be swapped into the context of a larger ongoing campaign. It provides a basis for resolving man-to-man combat and focuses on the individual character scale, where more prominent games focused on the scale of large armies. It was the first game to introduce elements of fantasy fiction such as mythical monsters and spell casting, and thus caused a revolution. As D&D became more commercially available, the gaps in the system and the need for other games' rules became more noticeable issues for players who weren't part of the Lake Geneva wargaming club, so Gygax and TSR released 3 supplemental books to fill that need. As such, to fully play D&D as its own game you need the original three books, Men & Magic, Monsters & Treasure, and Underworld & Wilderness Adventures, along with the supplements Greyhawk: Supplement I, Blackmoor: Supplement II, and Supplement III: Eldritch Wizardry.  The other two supplements, Gods, Demigods and Heroes and Swords & Spells are mostly unnecessary.

As I said earlier, D&D is a skeleton of a game and to truly play, you must flesh out the campaign yourself and add in your own game rules and campaign ideas. Fans of the system see this as its greatest strength, in that you're allowed and encouraged to let your imagination go wild and add in whatever you want. Dave Arneson, the co-creator of the game, did just such a thing with his Blackmoor campaigns, which brought in elements from Chinese wuxia films, space age science fiction weapons, nuclear power and whatever else.

But in my view that means that you're not playing D&D, you're creating and playing your own game with D&D as a guide. In effect, you're house ruling and homebrewing it all yourself. And that was the intent all along, and its greatest draw, and also how its creators actually played. Gary Gygax himself admits that he basically only uses some tables and math resolutions, and prefers to just do everything else on the fly at the table.

If I had to do that, though, why would I play D&D? Why wouldn't I just make up my own RPG system without the wild inconsistencies and issues of D&D? With Blackjack, and hookers. If I had to homebrew it all, I'd rather just homebrew a whole game myself. Which I guess is what happened after Wizards of the Coast released the Open Gaming License.

This sentiment that most players weren't playing D&D but their own game that was mechanically very dissimilar to the original was echoed by Gary Gygax in his introduction for Advanced Dungeons & Dragons. There was a backlash of that from the fans, but I think there's some truth his statement.

D&D's greatest strength is that it created and introduced the idea for Role Play gaming, and provided the beginning framework on how to do so. I find it strange that, once this idea became globally available, its fans started to just try and 'improve' D&D, rather than create their own better systems wholesale. D&D isn't all that role play games could be - after all, Vampire: The Masquerade is very different from D&D and yet is a popular role playing game in its own right.

Dr. John Eric Holmes famously studied the core booklets of D&D before coming to the conclusion that the game was "impossible to play" as written, and created his own revised version of the game called Basic Dungeons & Dragons, published officially by TSR. Other players not from Lake Geneva, WI came to the same conclusion and created their own spinoffs as well, such as Tunnels & Trolls.

Advanced Dungeons & Dragons is a much more feature complete game than D&D. It's meant to be an end to end campaign system in itself, without the need for mandatory supplements in order to be played. In a way, it's also more restrictive than the original game and is much less modular, as adding elements from other fiction or from other war games will break the already skewed balance and can actually change the nature of the game. And a phenomenon it shares with its predecessor is that AD&D also needs to be house ruled before it can effectively be played.

There exists a community of players that still enjoy Original Dungeons & Dragons, and still rank it as their favorite version of the game. I think that they do so because it was the first game that they played, and not on the intrinsic merits of the system itself. As a modern player, there's very little reason to go back to OD&D except as a historical curiosity. There are so many revisions, future editions, spinoffs and clones that fill the shortcomings of the original game that there's no real reason to play the first by itself. If players really want to homebrew their own game, the easiest method would be to use the d20 SRD and create one that way.  As a lover of history and hoarder of childhood antiques, I can see the appeal of wanting to own and play original D&D, but functionally I cannot recommend it above later, successive editions of Tabletop Role Playing Games.

My current experiment is to play Advanced Dungeons & Dragons as written (if not as intended) and in doing so I've realized that there is a very specific style of play it encourages, and a solid vision to the game. It's not a very strict system, but changing either changes the nature of the game, and I fully encourage players to do so to find the style of game and the vision they like the best and want to play.  I believe the reason that so many old school players, 'grognards', dislike the modern edition of D&D is because it really does replace both the style and vision of AD&D with something else, something a lot more forgiving, consequence free and wildly fantastical

My favorite overview of OD&D comes from this site: https://thealexandrian.net/wordpress/2603/roleplaying-games/reactions-to-odd

High praise for the open ended, freewheeling nature of OD&D from the OG http://kaskoid.blogspot.com/2016/02/how-i-helped-to-pull-rope-that-tolled.html

and an actual mechanical comparisons of the two systems: http://deltasdnd.blogspot.com/2012/02/damn-you-gygax-part-1.html