I read the book once when it came out. Since then I've had the chance to reread it a few times, discovering more and more layers as my interests take me in new directions(for instance the discussion on the happiness treadmill goes to the core of the current discussions in the economics of happiness). I now carry a copy on my trips as I can kill time in airports by perusing random sections.
The book is so readable as to perhaps set a standard. Yet it is complete in the sense that it covers more of the evolutionary thinking than meets the eye. I didn't realize it until I went to the site [...] and got into the more technical research material.
Reread it.