I should point out that I disagree deeply with some of the reasoning and theories in this book, and in general, think most arguments surrounding biological determinism are misguided (if not downright dangerous) but, I do think Ridley raises some good counterarguments to prevailing "nurture-only" arguments that currently prevail societally and warrant consideration and debate.

That said, I think his early sections on "Why sex?" and "Why sexes?" are infinitely better than when he starts to foray into what I think is mostly a survey and weaker thinking on human nature being defined by sex and feels he cherry-picks overly to support his case.

So, strangely, I think he fails in his premise, explaining human nature through sex and evolution, but does a really interesting job building the cases for sexual reproduction and the existence of genders.

Worth the read, but should be read very critically.