There was another thread that popped up about this, and it was fairly decent, so I will copy paste the replies here:
There are many critiques of this book, it's very controversial, but good read non the less. I think you should read it and then read some critiques. There are often threads on /his/ about it /lit/ and /pol/ also love to hate it.
You can find a bunch of reviews and critiques of it with a little bit of googling, so I recommend read it, think about it, and read some critiques.
The author himself is not a Marxist, but from what I can gather, the book is a decent layman introduction to the concept of historical materialism and how it can be applied as a lens to assess the comparative development of civilizations. Unfortunately, some of the claims made by the author are backed by research that's more than a bit shoddy, and reactionary critics love to pick on the book for that reason, but it's pretty clear most of their ire stems from the fact that they are uncomfortable with having their racial essentialist worldview attacked so directly.
I agree with other posts here.
Think of the book as part of a dialectical process: Its a way to begin to think in materialist terms.
While it is a little bit geographically determinist and a has liberal bias in favor of competition as a being a good driving force in society (toward the end of the book), it can help you start to consider that there are material conditions that at the very least provide a strict constraint on what can happen in human society.
eg. you can't get metal weapons in an early agrarian society without easy access mineral deposits
I recommend reading it alongside book like the selfish gene (Richard Dawkins) & Bad Samaritans (Ha-Joon Chang), as far as non-marxist authors go.