As self-help books go, this is undoubtedly one of the better ones. It also avoids the trap of anecdotal "evidence" so common in books like The Power Of Positive Thinking by Norman Vincent Peale, and instead uses a solid proven scientific platform written in accessible language without too much dumbing down (a difficult balancing act), structured sensibly each with an associated action plan to change behaviours for better outcomes, and indeed acknowledges its own debt to CBT methods and research in the process.
Like almost all self-help books it is also deeply flawed, primarily for two reasons. The first is that the human inclination is not to read these books cover-to-cover a chapter at a time and enact where mentioned but to dip into the relevant sections at the time of greatest need, then to discard almost immediately thereafter. Unless such advice is linked to a systematic support process it carries almost no chance of sustained success. Many chapters in the book may add value to people who are stressed and anxious (eg. Anger, Self-Efficacy, Distress, Unhappiness, Self-Esteem, Relaxation Techniques), but the chances are anyone in that position would not have the patience to try one at a time and may well head straight for Relaxation instead.
The second weakness is the tendency towards self-publicity on the grounds that it wants to sell more books. Granted that if it did not sell copies then the value of techniques described would be blowing in the wind, but you can't read self-help books in general without feeling you are being chatted up by a snake oil salesman. Maybe such volumes are self-esteem therapy for the writers every bit as much as the reader base?
"This book aims to empower you" declares one section, and then goes on to declare that if it were regarded as not being rocket science, that would be a job well done, the other risk being that it is teaching grandmother to suck the proverbial eggs. As I say, it is a difficult balancing act, but the language can on occasions tend towards the patronising.
I hope it brings you success in managing your moods anyway!