This is a thorough work in historical theory. The author begins by presenting a few theoretical postulates (especially relating to inequality in economic distribution) and then proceeds to analyze hunting-gathering, horticultural, agrarian and industrial societies to support his theories. He utilizes anthropological research and also seems to have a good enough command on world history to construct meaningful theories. I liked the chapters on horticultural and agrarian societies in particular. However, his analysis of industrial societies was much less interesting. It is by now badly outdated (the book was written in 1966) and quite incongruent with the rest of the book. Whereas the early chapters build on general historical information, the arguments about industrial societies are based solely on random statistics void of general interest. It's still a good book with some great insights, but in my opinion it would have been better if the chapters on industrial societies had just been left out.