A few years ago we ran a campaign with the Holmes rulebook. We customized the rules a bit. Our house rules have finally been written up as a PDF and are available for download. I'm calling them the Lost Book of Holmes.
We are biased because of when we started playing, but we like the Holmes rules. There isn't any bloat there. While it's true characters are limited to 3rd level, most of the monsters are there, even if you can't hope to fight them.
The Holmes Companion fixes the level limitation. The author of the companion is minimalist and fits his additions into 4 pages. Like the Holmes rules themselves there isn't any bloat so we used them as a starting point for our house rules.
Our campaign was run with the Holmes rulebook, a printout of the Holmes Companion, and few pages of handwritten rules.
Our first rule addition was variable weapon damage. In Holmes every weapon does d6 of damage, which is simple and befits a beginning version of the game. However, we like variable weapon damage. It makes the players think about trade-offs such as do I use a shield or a two-handed weapon? Should I be a fighter who can use the best weapons, or should I be a cleric or magic-user?
Universal d6 damage is perhaps a throwback to a time when the polyhedral dice were hard to get, but the box set came with the dice as you will remember.
We also removed the rule in Holmes where daggers strike twice a round and two-handed weapons strike every other round.
Although we did not use it in our play, the Lost Book of Holmes includes a optional WEAPON ADJUSTED COMBAT section in which all hits do d6 and the attacks per round of daggers and two-handed weapons as in the original Holmes rulebook are used. To make this sensible a variety of "to hit" bonuses and penalties are introduced.
We used d6 dice for monsters. I'm not sure how I feel about that in general, but we played with a small party so it worked well in our campaign. Incidentally the manuscript Holmes submitted to TSR used d6 monsters. The d6 dice for monsters rule is removed from the Lost Book of Holmes, however, to be compatible with the Holmes rulebook that was published.
We added to the list of monsters. The Holmes rulebook doesn't have many monsters a party might encounter in the wilderness. The Holmes manuscript shows they were originally there, so we added them back. We also added elementals, efreet, and a few more dragons. Monster descriptions were taken from the Holmes manuscript, OD&D, or the 1977 monster manual.
So the players could go deeper, we expanded the WANDERING MONSTER TABLE from 3 to 6 levels.
We added rules for generating NPC characters. If you look at the description for Bandit, you will see some short rules for generating high level NPCs. These rules call for a magic-user as high as 11th level! Anyway, generating NPCs quickly is something published versions of the game have never provided good rules for. The tables cover alignment, class, race, level, weapons, armor, equipment, magic items, and even names.
We added rules for brawling, capturing, mounted combat, and sea battles. Each of these was motivated by a specific encounter in the campaign.
That summarizes our house rules, but there are a few more extras in the Lost Book of Holmes:
- WILDERNESS ENCOUNTERS
- TOWN ENCOUNTERS
- RANDOM DUNGEON GENERATION
- SAMPLE WILDERNESS
- SAMPLE TOWN
We had equivalent stuff for some of this in the setting I ran, but I wanted Lost Book of Holmes to be a bit more generic. The SAMPLE WILDERNESS and SAMPLE TOWN are supposed to fit with the Sample Dungeon from the Holmes rulebook.