The book is divided into three major parts: "Let Slip the Whores of War!", "The Evolution of Depravity", and "Are Men Necessary? Usually, but Not Always." Within each part are several chapters, each on a particular theme.
Here's the first question in the first chapter.
"Dear Dr. Tatiana,
My name's Twiggy, and I'm a stick insect. It's with great embarrassment that I write to you while copulating, but my mate and I have been copulating for ten weeks already. I'm bored out of my skull, yet she shows no signs of flagging. He says it's because he's madly in love with me, but I think he's just plain mad. How can I get him to quit?"--Sick of Sex in India
Who'd have thought a stick insect would be among the world's most tireless lovers? Ten weeks! I can see why you've had enough. Twiggy, your suspicions are half right. Your paramour is mad, though not with love but with jealousy. By continually copulating he can guarantee that no one else will have a chance to get near you. It's a good thing he's only half your length, so he's not too heavy to carry about.
The answer goes on, giving more examples interspersed with explanations of evolutionary biology. The book is hugely entertaining, as well as informative (the book has 308 pages and pages 235 to 297 are devoted to notes and bibliography). Most of the book is written in Q&A format, which makes it easy for us non-biologists to avoid being overwhelmed with the huge diversity of sexual behavior in the animal kingdom!