This book was recommended to me by a practicing clinical psychologist. I was very disappointed with it. The author claims to be targeting both professional and retail readers but in my opinion doesn't succeed in doing either very well. It is a fairly long book but the essence of what the author has to say could have easily been conveyed in a well edited 100 pages with perhaps an extensive appendix of the many ACT techniques that he mentions throughout the book with a summary of evidence for the claims about these techniques. For a book claiming professional and scientific integrity, proper and credible proof of claims was sadly lacking.
Early in the book, Heyes states that Acceptance and Commitment Therapy (ACT) is heavily based on Cognitive Behavioral Therapy (CBT). He further states that the extensions to CBT which ACT offers are based on ancient spiritual practices such as meditation and mindfulness. These claims seem reasonable and would be interesting if properly explored. Instead we get dozens of stories about these techniques but little in the way of valid evidence to support most of the them.
More conservative research about ACT techniques suggest that they work a little better than conventional CBT in some situations and a little worse in others.
As the book progresses, Heyes' claims become increasingly ambitious. Towards the end he is more or less saying that ACT will cure anything from warts to cancer.