OSRIC is of course a hugely useful tool, but I agree with prior posters that Gygax's original language is enchanting and enjoyable and rewarding, so the original books are definitely worth reading.
If your game includes life-draining undead, you might want to fiddle with that as well. While it was VERY effective at instilling fear & loathing, the level draining system could dramatically slow play down. Players had to essentially “deconstruct” their PCs on the fly to figure out what afflicted PCs could still do.
In 3.X, I contemplated replacing level draining with using the game’s fatigue mechanics. It worked conceptually and still had meaningful, scary effects for all classes. And there fewer character changes involved, so it was less likely to significantly slow gameplay.
I actually liked the 3.x level drain mechanics quite a bit for speeding play while retaining the fearsomeness of level drain.
Every character or creature has a number of Life Energy Levels equal to its level or HD. Each time a level drainer hits you, you suffer one or more Negative Energy Levels. When you get one of those, your max and current HP are reduced by 5, you lose your highest level maximum and highest currently-prepared spell, and you take a -1 penalty to attacks, saves, skill checks and ability checks per negative level. If you get negative levels equal to your level or HD, you're dead (and likely going to spawn as that kind of undead).
Restoration and Greater Restoration can get rid of negative energy levels. If you don't get them soon enough, 24 hours after getting a negative energy level you get to make a Fortitude save for each negative level (DC varies based on how powerful the attacker was). Any successes go away. Any fails become actual lost levels, adjust as needed. Which can be some work, but you're not doing it in the middle of a fight.
I've strongly considered back-porting this rule into my old school games.
Simple fix for that is to have players record their h.p. etc. at each level along with what spell slots were gained, such that when a level is lost they immediately know what to drop back to.
We always did this back in my AD&D groups. Write down the individual hit point rolls for each level. Spell slots you can always recreate by looking at the charts.
The Monster Overhaul has a sidebar with alternatives to level draining that's worth checking out. The simplest is just applying an XP penalty to make future levels harder to achieve. Still a potential character-killer, but it doesn't grind play to a halt as everyone figures out what their character is still capable of doing.
Another good part of that book.
Dyson Logos also did an
article with alternatives to level drain back in 2011. An updated version of the article was printed in the first issue of Knock! as well.
From what I remember, there are no variations between printings of the books. Besides the Cthulhu Deities and Demigods. The content is all the same, only the covers are different. So whichever cover looks best to you, get that one. Or, if you have a PDF editor, buy whichever version you can and slap the cover you like on the PDF.
Stick with the core three for the rules and skip the other rules supplements. It will make things drastically easier to deal with. But pick up the other two monster books, MM2 and Fiend Folio.
No one ever actually play using all the rules printed in the books. No one. A lot of people online claim to have played all the RAW by the RAW, but I've never met an actual person in meat-space who's ever made that claim. Most people used the character races, classes, arms and equipment, and spells sections of the PHB but not much else. The absurd tables of weapon speed and weapon mods vs armor types were never used at any table I've ever heard about in meat-space.
People will inevitably bring up ADDICT and point to it as some kind of AD&D bible, it's not. It's a product of later players obsessed with RAW scouring every possible source to find every niche bizarre rule ever printed and smashing them all together. Again, literally no one played that way. When AD&D was new, D&D was still very much a folk tradition rather than an official RAW worshiping scene. It was only later that people began worshiping RAW. Actual AD&D players at the time when it was current used what made sense and ignored the rest.
It's not a bible. It's just a really detailed tool for understanding and putting the entire AD&D initiative system as printed in the DMG, including special cases like potion onset times which are buried in the potion rules, in one place. Some people ignore the entire AD&D initiative system and just use the B/X one. Some people use MOST of the AD&D system and ADDICT is a handy tool for figuring out what all the pieces are and which ones you want to change or ignore. Consciously. As opposed to just doing it from the DMG, which will inevitably mean the reader will miss details or misunderstand them.
Context for what follows: I love multiclassing; I don’t follow OSR gaming at all, so I don’t know what has or hasn’t been done.
If I were taking on a project like this, I might consider eliminating multiclassing and reworking the classes (availability and design) to make it relatively unnecessary.
By that, I mean expanding the number of classes available, but simultaneously making each class more focused but with increased customization options. Good 2Ed examples of this included the kits and the Players Option books- especially what they did with the cleric.
You’d start with your core 4: some kind of thief, some kind of warrior, some kind of full arcane caster and some kind of divine caster. (If you wanted, you could add a full psionicist.)
Then you’d make a few hybrid classes: a fighter/thief; half-caster combos for rogues & warriors with each of the caster types; some kind of pure caster hybrids combining 2 types each (probably with half-caster progressions) .
This is a good approach, though a lot of work. I'm extremely fond of the simplified approach Dan "Delta" Collins used in his
Original Edition Delta, which is a set of house rules for OD&D but the multiclassing rules could be ported to AD&D with no or very little change.
