Guns, Germs, and Steel: big question, long answer

Why did some parts of the world end up conquering others? It's a huge question and Diamond's answer is mostly geography: which plants and animals could be farmed, and which way the continents run. It really does change how you look at a world map.

It's also repetitive, and historians have serious criticisms of how much it leaves out, especially what people themselves chose to do. I'd read the first third carefully and then skim. It's still one of those books that rearranges your head a little.