I've been doing ACT for a couple of months now, and I'm not quite all the way through "Get Out of Your Mind...". In theory, it makes a lot of sense to me. I think it's going to take a little time and a lot of effort to see major results, but I'm already having some small victories.
I've tried CBT, but it's not been for me. It's possible I've never had a decent CBT therapist. Three times that I can remember, I've started with therapists who have promised CBT, and after several months, I realize we've been doing nothing but talking. I had one guy who was a serious CBT dude. He was such a dick, we never got beyond, "Go home and exercise." (Here's a clue, Sparky: If I could just go do it
, I wouldn't need therapy)
ACT is more about taking myself out of my comfort zone, which is obviously something a person with major league avoidance issues does not do well. But the approach in the book REALLY helps me to begin doing just that.
So that's a little about my experience. I wish I could do a better job of defining it, but I think you can find a lot of good info online.
Here's the book I'm using: Get Out of Your Mind and Into Your Life
I would highly recommend going through it with an ACT therapist. Reading it on your own is not going to be as beneficial, IMO.