Given play centered around a multi-hundred page rules text, 90% of play will actually use only 10% of the official rules, and pushing play into that other 90% of rules will only produce about 10% as much fun for the participants.
Thus I regard traditional "big book" roleplaying texts as inherently ... futile, I'll say. I've never actually observed, in one-shots or campaigns, either as a player or GM, a big-book rule system that didn't in practice get whittled down to little more than just action checks, damage rolls, and whatever few broad-strokes setting points were needed to justify the wild schemes and monster hunts the players always ended up pursuing (in other words, about the same thing as a twenty-page rules-light system). Note, I don't think there's anything wrong with playing this way; in fact I feel accepting this practical upper limit on mechanical consensus only make things better for everyone involved. But somehow, despite all this, the commercial counterpart to this hobby keeps finding an audience for big texts that I think are mostly going ignored.
Perhaps I'm blinded by my preferences; I openly prefer light games, minimal stat-lines and lots of room for at-the-table improvisation and rulings. And I admit, I've heard second-hand of people playing mechanically expansive games like Burning Wheel and Champions with all the gears engaged. But I've played Burning Wheel myself (run by the author no less) and in those sessions, we ignored most of the small text on the character sheets and just threw dice like most other games.
A caveat I'll allow is that there's usually at least one participant who is very much into something in that outer 90% of rules. A player who's all about the magic system or another who's all about the personality mechanics, or a GM who dives into the tech-building processes. but those are effectively sub-games maintained by just those people; the group as a whole doesn't engage with those rules any more than is needed to validate the enthusiasts' contribution to play.
|A tiny little book about vampires, from the blog On Being a Mini Mum.|
Because something something rules light.