The introduction notes that players "create their own map as they explore," which is important, in my opinion, as it emphasizes the exploratory nature of dungeon delving. Miniature figures are mentioned several times, both in the introduction and in the "How to use This Book" sections. The text says
The game is more exciting and spectacular using the lead miniature figures mentioned above, which can be painted to each player's individual taste, but paper markers or chessmen can be used effectively.There's lots of evidence, as we'll see, that Holmes didn't think miniatures were necessary for play, but their presence, if only in a very abstract form, seems to have nevertheless been assumed as the default for most groups.
Holmes offers only 3D6 in order as a means of a character's abilities. Choice of class should be influenced by the results of the 3D6 rolls but is not bound by them. Strength has no mechanical purpose in Holmes other than as a fighting man's prime requisite. Intelligence grants knowledge of additional languages, as well as being the magic-user's prime requisite. Wisdom serves only as the cleric's prime requisite, just like Strength. So far, the abilities function exactly as in the LBBs. Constitution grants bonuses to hit dice rolls, as per Supplement I. Dexterity serves as the prime requisite for thieves and grants as bonus to hit with missiles, as in the LBBs. Although mention is made in the description of Charisma of followers and their loyalty, there are no actual rules to handle this in Holmes. It's worth noting that Holmes follows the order of abilities given in OD&D, with CON coming before DEX, rather than the reverse as in AD&D.
Prime requisite scores can adjusted upwards by sacrificing points from other abilities. The exact formulas by which points from one ability get converted into points from another varies by ability and by class, but it's generally at a ration of 2-for-1 or 3-for-1. These formulas are generally the same as those in OD&D but there are some exceptions, such as clerics no longer being able to lower Strength to gain Wisdom, for example. DEX cannot be lowered but it can be raised by thieves. CON and CHA cannot be altered at all. Unlike in OD&D, where it's implied in at least one case that these alterations to ability scores apply only to earned XP, there's no such implication in Holmes.
Character classes available are fighting men, magic-users, clerics, and thieves. All four are described as being primarily human classes, though it is noted that dwarves, elves, and halflings may be thieves, though no rules for this are presented. Instead, the reader is referred to AD&D, so it's a bit of an option question as to whether Holmes support demihuman thief characters. Demihumans throughout the text are generally treated as fighting men, although elves are noted as being "a combination of fighting man and magic-user." Thieves must be either neutral or evil in alignment, but the other three classes may be of any alignment.
Dwarves have infravision, while elves merely "see ... in the dark." Elves are also immune to ghoul paralysis, something not mentioned in OD&D. Elves in Holmes seem to function somewhat like a proto-AD&D multiclass character, but the text is unclear.
Elves progress in level as both fighting men and magic-uses, but since each game nets them experience in both categories equally, they progress more slowly than other characters.I would assume this means that XP is divided equally between the two classes but I can imagine someone arguing that that's not the case. I wouldn't allow such an interpretation in my campaign, however. Complicating matters further is that elves use D6 for hit dice, though it's never specified when an elf gets new hit dice, since they have two classes. Halflings, despite being fighting men, get only D6 for hit dice, owing to their small size, thus opening up the notion that hit points represent, at least in part, body mass. Holmes uses Greyhawk-style hit dice and allows for 1-3 hit points regained per day of rest as opposed to OD&D's mere 1.
The list of equipment and weapons in Holmes is identical to that in OD&D, right down to the prices and the inclusion of wooden and silver crosses rather than more generic "holy symbols."
Under "Additional Character Classes," Holmes explains that AD&D introduces more character classes and races. These include half-elves (but not gnomes or half-orcs), paladins, rangers, illusionists, monks, druids, assassins, and witches. Mention of the latter class is original to Holmes, as Gygax denied in various places that there were ever plans for a witch class in AD&D. I can only presume, given Holmes's mention shortly afterward of "a Japanese samurai fighting man" that he was assuming that some of the classes in the pages of The Dragon at the time, of which the witch was one, might make it into AD&D. There's also mention of psionics and the possibility of unusual character types at the DM's discretion.