It's confession time. I have a bad tendency of late of not reading the setting material in the supplement books for the games I run. Not that I don't like the settings, but for the most part I don't have much time where I can pull out a giant RPG book and just sit and read the fluff. When I do get to read the material I usually like it, and generally find a few things I can use but even then I find I discard a lot of the stuff in favor of keeping the game world my own.
Today's discussion is this: when running in an established setting how true to the books do you keep the world? Obviously you have to branch out and do things yourself some of the time, but do you try to keep close to the books? If a supplement comes out after you've began running the game do you incorporate the additional setting details quickly?
For that matter, how many of you - especially the ones who make the world your own - bother to read, or enjoy reading, the setting fluff in these additional books? Obviously there is a large market for it, but I'm curious how many care more for the mechanics/player options that players may want in their game and less about changing the world once the game is already in motion.
As usual, sound off in the comments.