In years of teaching, I have found that many people don't really know how to practice. This book is designed to help provide direction, focus, and long and short-term goals that help make the most use of practice time.
If you know someone just starting band or just starting lessons, this is a good way to start. It's equally useful for more advanced musicians.
In using it with my own private students, I have found that those who use the book do progress more quickly and seem to gain a greater enthusiasm for playing, as they see the progress.