I have two "barbecue" cookbooks on the bookshelf in my office that I refer to often. Both of them have been suggested in this thread...
Adam Perry Lang's Serious Barbecue
Andy Husband and Chris Hart's Wicked Good Barbecue
I should note that I own almost every barbecue book that is available (meaning in print now, and not self-published), and we have just about every book suggested here for sale in our store, but these are the two I love. Adam Perry Lang has a newer book called Charred and Scruffed that I really like as well.
eCommerce, Marketing and Media Director for All Things Barbecue
Yoder Smokers YS640 (on Silver Comp Cart)
Yoder Smokers Loaded Wichita (Serial Number 1)
Weber Kettle 22.5" Silver (w/ Smokenator, KettlePizza, Smoke•EZ, and more)
Ninja Turtle Green Thermapen