Human biology for the layman
Anthony Smith writes clearly and lively. The book can be read from end to end or skip to the chapters of interest. Richard Dawkins has a similar style and ability to give a summary of complicated biological events in an interesting and informative manner for the layman. Written in the 60's you can now see where his prediction were right or wrong.
Only half the people alive at anyone time actually reproduce. Take your ancesters back one or two hundred years and it becomes clear that we all came from a very small pool of people. I'll leave Anthony Smith to explain the rest.
Recommended for youngsters (and oldsters) for information about the facts of sexual life.