I just got done watching Indiana Jones and the Last Crusade. In the movie Indys father kept a diary full of clues to finding the Holy Grail, which of course is used throughout the movie.
I was thinking that would be a cool game thing. Not an in-game book, but a real book included with the game itself. The basic manual would be separate and small (which manuals tend to be), but with that would be a book full of drawing, directions, clues, and other lore related stuff. The game itself would be very hard or impossible to beat without this book. Of course its not a cheat book or guide, as all the stuff is in passages and poems and other cryptic fun.
I'd love to be playing this game, coming into a room that seems impossible and seeing a statue in the corner and thinking "Hey, that looks familiar" and paging through the book to find the scribbled drawing of it, reading the passage and then figuring out exactly what I had to do based on the passage.
Ok, I'm probably totally alone on this one. Maybe thats the game *I* need to make.