For the reader looking for a good self-help book, this book has a lot of great information and truly can help you live a more satisfying, more free life if you take the most basic points of this book seriously and work to apply them in your life. However, I think for a lot of people, the points in this book would be hard to 100% apply without the support/assistance of a personal therapist to help a person be truly successful with it, but that may not be true for everyone.
For the helping professional, it is an easy-to-read, easy-to-understand book on Choice Theory, formally known as Control Theory. Much of it makes a lot of sense and can be applied to working with clients in many situations. There may be some parts of it that a professional may disagree with (as I did), but I think the basics are good and can help professionals help people more quickly and more effectively than some theories out there. I think it is a worthwhile book for any counselor, social worker, school counselor, pastor, anyone in the helping field to read and use to help others.