So, I've been reading Grognardia over the last few days, specifically the posts related to the "Dwimmermount" Campaign, and it has hit me like a ridiculously specific polearm to the forehead. I had brushed up against the "Old School Revolution" before, and found some things to like there conceptually, but this series of posts is what really hammered home the ethos and the virtues thereof to me.
James Maliszewski's aim was to perform the gaming equivalent of historical re-enactment. He wanted to start with the D&D rules as originally released into the wild, and as much as possible, only add house rules and setting details as they became important in play (with some initial things to go off of, of course), much as the game went about its business between the publication of the original D&D box with the publication of Advanced D&D.
The things that especially amazed me were a) his focus on play as the the whole damn point, b) faith in abiding by the rules, however harsh, and the emergent drama that would result, and c) detailing things as they come up in play, and not before. Taken together, these things created an extremely compelling vision of play that I would love to try to emulate.
Don't worry, Book of Threes is still in the works, this is just something else that excited me.