I'm a teacher, nothing to do with acting, but I saw the book at the Royal Shakespeare Company in Stratford, bought it, loved it, and bought another online for a friend, also a teacher.
I was seduced by the blurb, and can now say it's true: "[It] is no more for actors only than The Art of War is reserved for warriors..."
When I'm teaching, I try to listen to the student, find gaps in their knowledge and work from there, rather than having a set agenda for a lesson, or even a course right from the start. This book resonated with this approach, and I got a lot from it, despite not thinking of using it for acting. I want to read it again, which is a good sign.