This book is fantastic. Now, it is not a "read this and you'll know how to ride" book. And that is a good thing! Afterall, if that was all it took, the world would be full of professionals! It is also NOT a book on how to train your horse. What this book is, is a great guide to improve your skills, so that you may learn to become a better rider and train your horse more easily.
For instance, most people know that they should sit a certain way and be "glued" to the seat. This book shows and explains how, through anatomy pictures and visualizations. It's kind of like Dressage meets Science meets Meditation. Everything is explained throughly and plainly.
I reccomend that all of my students buy it and read it.