While this book was really informative and entertaining, and I'll definitely be using it for worldbuilding reference, there are a few things that kept me from giving it five stars:
* The jokes got a little repetitive. But if you spread out the reading over a few months this is fine.
* There is precious little social science, which I thought was a pretty glaring omission considering North's training in linguistics. Where is the advice about how to build coherent, healthy societies and families? How to prevent income disparities and provide universal education? We're trying to build a civilization here!
* Some of the science he includes is out of date, or reflects commonly held assumptions instead of the latest research. For example, he suggests that farming is essential to prevent famine and reduce the amount of time you have to spend gathering food, but really a better way to prevent famine is practice birth control, and farming is extremely labor intensive compared to gathering berries and shellfish. Also, he argues that humans didn't invent language (language!) until about 50,000 years ago, which is extremely speculative at best. I won't go into it all here, but a linguist really should know better.