The book pushes back against the cynical narrative that we humans are selfish beings, that we only do good when it serves us. The narrative that said that the Stanford Prison Experiment revealed what being human is etc. (Stanford Prison Experiment's results were coerced and the study isn't valid, which i learned from this book)

He is right to push back against it but he goes too far, he says we are the opposite, that we are by default good, he picks instances of good behaviour and attributes it to our nature, he picks instances of bad behaviour and attributes it to a mismatch between our nature and our environment. Which results in the first half reading like Motivated Reasoning which I would say it is. If the first half was saying that we are neither good nor bad, we have potential for both and the environment brings out one or the other, that would have been more nuanced and closer to the truth and the second half of the book still would work well.

The second half of the book (maybe it's the last 2/5th) is very good, he points out all the cases/laws/norms that stem from the extremely cynical narrative about human nature and shows instances of environments which bring out the better parts of human nature. He points out what goes wrong when we act bad and how to increase odds of betterment.