I agree with Flaco that Walsh's book is a must-have. Not only does it have great recipes and techniques, but it also has interesting history of the different origins of Texas barbecue. But, it focuses on smoking meats for long periods of time, rather than "grilling." If you want a good, general resource for grilling, try this:
I bought Legends a few years ago, but am just now getting around to reading it. It is great for the history of Texas barbecue, but I personally find it lacking in useful guidance for someone who wants to master the craft. There are a few good tips to be plucked from its pages, but I expect that there are better reads for learning how to be backyard pit master.
I agree on the Legends book. Don't get me wrong, it's a great read, but there are better books out there on smoking.
For grilling, I actually like the Weber books (but maybe it's my bias against Raichlen --- though I do admire a man that gets paid handsomely to simply grill).