Very thought provoking. Focusing on behavioural psychology and neuroscience, but with a lot of animal observations as well. Written in plain English. I can't vouch for all the science in this book, but Sapolsky discusses both the experiments and the critics and seems to err on the side of caution in his interpretations.
I learned a lot from this.
It's a big book, in fine print, it should count as two towards my target. The footnotes are especially hard to read if your eyes aren't good.