OK. I am going to take a we bit of a different approach. All the books mentioned are great but they are just exercise books. Exercises are meaningless unless you know what you are supposed to get of them in terms of moving your technique forward. Even more important is "how" the exercises are to be done. I would get only two books. First, is the Irons book as suggested. The reason is that it is the only book that illustrates and explaines exactly what you are supposed to do with your tongue in terms of creating an arch to play higher notes. Second, (not not second) is "A comprehensive Practice Routine for the Aspiring Brass Player" by Don E. Johnson. He takes exercise complied from many of the books already suggested and explains in detail how to do the exercises and what you are supposed "feel" as you do the exercise. And, he take a progressive approach for each example, so if you are a beginner you have a decent place to start. The routine that he assembles helps you to cover the basics then expand as you improve or have more time.
Getting all these books can be overwhelming and give someone the feeling of not knowing where to start and how to proceed. Don Johnson's book will help you put it all together.