When I restarted piano a decade ago and before I had a teacher, I downloaded some book by Les., worked with one idea, then had a teacher and haven't looked at it since. The idea I tried then was that a student should have a physical feel of what to do before starting to work on music, and there was a particular exercise of pressing a single key while having the wrist move up and down. That was the impression I got then. That particular activity made sense to me, because while you concentrate on the wrist staying mobile, you are also not learning to keep your wrist (and arm, and hand) ultra-tense, as one is wont to do. In fact, when I self-taught as a child using the old fashioned material passed on to me, I acquired a rigid immobile wrist and arm.
I just looked at what I downloaded then. It is written by someone who says what Les. did and said - maybe it's the one you folks are talking about, maybe another. As I read some of the material and look at some of the exercises, with the knowledge I have now, I might be able to apply those things in the manner they were intended. There are some clues that suppleness and responsiveness in the arms and wrist etc. were also intended. But I would not use this book for self-teaching. I could see a teacher who fully understands how the body and technique work at the piano, using this book, while guiding, and observing the student. Done on one's own, there is too much that could be misapplied in a harmful way. I don't know if it's the same book.
Topic: Your opinion and thoughts on a certain book