I reivewed Raph Koster's brilliant Theory of Fun book (think of it as an Understanding Comics for games) here before, and now I'm delighted to see that Raph's posted a tremendous, graphic-rich picture-book in PDF format detailing the notions from the game.
4.7MB PDF Link Better 4.7MB PDF Link
(via Wonderland)
Update: We killed a server with this one, there's a mirror of the file here