I read this book years ago while I was riding and showing dressage and jumping. I found the book well written and even though I do not ride at this time, I believe that any rider of any discipline would highly benefit from this read.
Years ago, where I lived at the time, I found much of the trainers to cap out at second level. The trainer I worked with at the time was educated by a woman who studied under Nuno Oliveira. Despite the differences in methods, I found that what I read and what my trainer focused on was easily cohesive.
This book is great and for those who find it dated, well, that very well maybe. I find the old school to be the best.