This is far and away the most usefull and insightful self help/therapy book I have ever used. I chose the word "used" over "read" quite intentionally. I did not use it in a vacuum- rather did it while in therapy with a trained ACT therapist. That isn't to say that it couldn't be helpful on its own. It is important that you do the activities and I believe it is essential to discuss with another your activities, thoughts and impression.
Let me finish with this. I sincerely believe in ACT- and I believe this is a great gateway into ACT.