At the last "ReadingClub" I heard really good review of this book and it convinced me to read it right away. It was a really good idea, because there is so much you can learn from that book.
One of the most important things that I have learned, was that, success is not happiness, and we are wired to strive for success and not happiness. What is considered success for person, group or humans as a species is not making us happy. It's not that easy to notice it in our culture.
Author created the metaphor of elephant and it's rider that is now well-know. I have even stumbled upon it a couple of times, but it was still good to read the full story as there is much more to it that I thought.
One of interesting things is that the elephant is not only our body and 'animal' part of our brain. It's also the 'self' part that gives us flow of thoughts, so it's normal to have ridiculous thoughts.
This hypothesis fits nicely to "The Power of Habit" as habits are in domain of the elephant, not the rider.
Very interesting is to read more about religions and why they are with us. Theory is- that they help groups work together and fight other groups. They connect but can also help differentiating from others.
There is a bunch of nice ideas how to make your life better by optimizing things that you can get used to and removing things you can't. One of those things is a bigger house that forces you to spend hours on your way to work or back home. You will get used to bigger house but you can't get used to long hours wasted in car or the bus every day. I really fail at this one and it makes me think where I want to live in the future.
Another thing is 'Flow' (as in book of the same title explaining this feeling of focus on a task) and I really think about reading it in near future, as there was not enough to grasp this idea fully. If you need sort explanation you should choose work that you can feel 'flow'. For example when you play a great game or you are programming something interesting. Your happiness might be higher if you have more 'flow' during the day.
That's it. That was my short review of "The Happiness Hypothesis".
If you are into positive psychology read it, you won't regret it.
Thanks Adam Szymaszek for corrections, I have corrected all that I remember.