This is easily the most important book I have ever read.
The book is meant to be read with a guide or a mentor, or at least a discussion group. This is necessary for many reasons- the least of which is that many of the ideas will have a profound effect on the way you begin to think if you do the thought experiments (with others) that go along with them.
I found that (within my group) it is common for people to grasp many of the concepts for themselves, and begin to apply them to their interactions with others. Some people will stall out half-way through the book because it can take time to process and assimilate what you are learning.
I find that this book is often a reference guide and 'go-to' handbook for many top coaches, executives, and thought leaders today..... but it is rarely referenced. I suspect this is because it is written to be used, and may be thought of more as a text-book than a best-seller- and is marketed as such.