2.75

Halfway through the author unapologetically gets repetitive. They could make the case that it improves retention, but it would've been more efficient in a easily memorized bullet list that he refers back to. 
There are some valuable sections, and if one is receptive to advice, anyone could benefit from seeing their personality as learned habits from early experiences that conditioned them to respond/perceive in negative ways. It's easy to fall into habits that put us into an auto pilot mode where we rely on memorized feelings instead of considering how a situation would look like with a different mindset. 

The early studies referenced are laughable and probably off putting for most. If you've dabbled even a little in psychology or productivity content, a lot of the second half will be really familiar.