The X in Sex: How the X Chromosome Controls Our Lives by David Bainbridge begins with the discovery of the X chromosome (by a man) and the Y chromosome (by a woman). From there it moves onto a variety of topics: the genes that control gonad growth, sex linked diseases and how human women are like calico cats.

David Bainbridge spends about a third of the book outlining many of the different ways that animals reproduce and how gender is selected. Although the XY (male) and XX (female) is the standard approach in mammals, there is even an exception among mammals. Of course birds, reptiles and all sorts of other non-mammalian animals have evolved different ways of reproducing. Despite all these different approaches, they all share similar genes to control the process.

Reproduction doesn't always work normally. Bainbridge discusses the ways in which things can go differently and what the outcome means for the offspring. My favorite part though comes near the end where Bainbridge compares the calico cat coloration to the genetic tug of war going on inside every woman's body.
The book is a fairly easy read for all the science that's included. It's written with clear and concise language. Sometimes I think Bainbridge lets too much of his own prejudices into the book, filtering all the information through the perspective based on his own upbringing. At least he's willing to admit this short coming in the book.