That's where my idea ends, having not read the books I can't really say where to begin, but I have played a lot of games with this type of style, Aliens vs Predator had this style, how about we base the rp in or near the climax of one of the books, and our characters can visit/ deal with problems that the main character didnt do himself. Kinda like walking behind someone, we go all the places they go (mostly anyway) and we end up reletivly at the Sam place the main character does, and why our characters do this is maybe, a bounty on the main character?