My long-standing suggestion has always been Smokestack Lightning. It is less of a cook book, more of a tome on the origins, history and contemporary interpretation of what BBQ is to us today. Getting back to your request, it is rich with recipes that were uncovered in the authors' journey through the south and west in search of the best BBQ. Definetly worth a spot on your shelf... next to the jar of dry rub and above of the sack of pine chips!!
I agree with foodnfoto, the Raichlen books are very good. For slow cooking (smoking) recipes and information, check out Smoke & Spice : Cooking with Smoke, the Real Way to Barbecue by Cheryl Alters Jamison.
Weber's Big Book of Grilling and its predecessor, Weber's Art of the Grill are good too.