Nettle summarises the various studies and statistics available on the subject of what make people happy. Importantly, he has a useful discussion on the types of happiness; feelings of joy, judging oneself to be happy, and realising one's potential. He focuses on the second, and crunches through the studies, also provding useful scientific explanations of how the brain works. Three of the most interesting things that stood out for me were that most people are actually happy, control within one's job is more important than income, and there is a distinct (biological) difference between wanting and liking. The latter is the root of addiction (and advertising), and also shows how getting what one wants may not lead to happiness.
I would have been interested in seeing a greater discussion on why the rates of depression are on the rise, yet most people are happy. Is it the case that the extremes of society are getting more pronounced? Or simply, we are more aware of depression than before. I also thought that his view that those who are neurotic (tendency to negative emotions) and introverted (closed to experiences) tend to be less happy was somewhat circular. This is the crux of the issue, that is, what causes what! Does being happy lead one to be less neurotic or the other way around?!
On balance, the book was informative, concise and life-enhancing