Thought I would list out a few barbecue cookbooks I think highly of.
How to Grill by Steven Raichlen. Covers plenty of territory, with setup instructions and photos for each recipe. Beyond the quality recipes, he includes small sidebar tips about what other foods would work with this recipe or other tweaks to the concept. These help a novice reader understand some of the underlying tehcniques of each dish and learn to think beyond the recipe. Some have dinged the book for the repetitive setup instructions, but that's more an issue if you read it through rather than pick it up to reference a recipe. In real use, the setup instructions are useful for beginners.
I consider his flavors of good quality. I think there's more that could be done with many of the dishes, but he plays it right up the middle which is a safe and reasonable approach for the purposes of this book.
The Grilling Encyclopedia by A. Cort Sinnes. This is a less well known book but one of my earliest grill/barbecue cookbooks. If you pay attention to the author credits, you'll see him crop up in Cook's Illustrated, and some other cooking magazines. It covers much of the same territory as Raichlen's How to Grill but touches on some oddball dishes and has some really good sides. I'll usually look at this and How to Grill if I'm attempting something I've not grilled or barbecued before to get the technique, tips and basics straight in my mind. Includes some ingredients you'll likely never have seen grilled before.
I give Sinnes the edge in flavors in his book compared to How to Grill with a good section on barbecue rubs and some pointers on building your own. That is a weak spot in Raichlen's book.
Paul Kirk's Championship Barbecue Sauces by Paul Kirk. Sure, it's a cookbook of rubs, sauces, mops and such. So recipes abound. But he also includes an excellent section on crafting your own which I found revelatory at the time I first read it. I think part of that was that he put down in writing some things I was doing unconsciously and intuitively by then. It's one of those books I read at just the right time for maximum impact. This book contains the best section on designing your own rubs I've read.
Championship Barbecue by Paul Kirk. This is recipe heavy and lighter on theory and technique. Still, there's such a breadth of ideas in it and he drops casual insight frequenty that it's worth going through even if you never follow one of his recipes.
Peace Love and Barbecue by Mike MIlls. Quite a bit of story and signature dishes by lots of the big names in barbecue. And plenty of good recipes too. This book is a fun read and brings together many of the great restaurant and competition dishes together in one book. Including some fun ways to re-work your barbecue leftovers like barbecue spaghetti, nachos and such. I enjoyed it as much for the stories as the food.
And for completeness sake only, Smoke and Spice by Jamison and Jamison. I only include this one as it's the classic text on barbecue. But it shows its age and I don't think the flavors are as good as the other books I've mentioned. It's still better than any of the other barbecue and grilling books they've written. Not one I would recommend today.