Luckily I’m allowed more than one, but if I could have only one, then this is the book I would choose. Howard Garret has been gardening organically in Texas since 1985. He has a website, radio show, and many other books (all of which are great!)
This book is a combination how-to and wish list of plants that do best in Texas. The pictures are gorgeous and he has specific information for growing many plants in our area. It includes a full range of organic solutions for almost any problem you can think of. It is simply one of the best all-around gardening guides, but especially if you are in Texas.