If you're already a hard-core jazz theory know-it-all, then you probably don't need this book. It doesn't have much in the way of advanced material.
But, this brilliant and well-structured book does cover a lot of material from beginner to intermediate-advanced, and any and every jazz enthusiasts, except perhaps the high-flying professionals, would have a lot to gain from it.
The structure of the book is more in the style of a reference, rather than a tutorial. I found this quite nice, since I can always find exactly what I'm looking for in the table of contents, and avoid reading over stuff I already know. If you're a more entry-level player, and would like a more tutorial-style book, I recommend the "Jazz Piano Book" by Mark Levine. "Jazz Piano Book" does cover less material than this one though.
If there is any room for improvement, I would say that it would have been helpful to see a list of essential listening that the authors recommend, much like the one included in the "Jazz Piano Book".