Borg wrote the bestseller 'Persuasion' but my suspicion is that he's a little stretched in writing this kind of book. There's nothing fundamentally wrong with the book. On the other hand, there's nothing to recommend this book particularly. There's nothing NEW or truly insightful about the book. The ideas are a rehash of the principles of cognitive behavioral therapy, ideas which have been written about in easy-to-use ways in other books that have been around for longer.
In particular, the author seems to use a lot of words to make his point, when I think that some of the techniques could be explained more succinctly. I don't know if I'm breaking amazon rules by recommending other books, so I won't. But there are other books based on cognitive behavioral therapy (Cognitive Behavioural Therapy For Dummies
and Brilliant Cognitive Behavioural Therapy: How to Use CBT to Improve Your Mind and Your Life
), which I have found more useful.