Well, I suppose the proof is in the pudding for how a reader is able to effect changes...
However, on first blush, I think this is well done and is a better synthesis of some of the concepts than can be found in many other books on the market. I think an important distinction is that book isn't necessarily pure self-help: it posits that understanding the origins and the concepts underpinning depression and some forms of depression treatment is important to effecting change.
I appreciated that O'Connor was self-effacing and seemed to thoroughly revise the updated version of the text. His discussion of SSRI's and other medications, in light of recent developments, also felt very realistic and fair.