My girlfriend and I both found the book Brain Sex quite fascinating, and began looking around for other books about the science of gender and sexuality. Bonk turned out to be a bit of a bunny trail, as it focuses more on the act of sex itself and the scientific ventures that seek to make sex better rather than the biological, chemical, and hormonal machinations of sexuality and gender. Nevertheless it was an interesting read.
Roach writes in an easily approachable style, but at times her humor is a bit cheesy and gets in the way of the science. There were a number of sentences and paragraphs that struck me as particularly clumsy, too, but that's a relatively minor quibble. Chapters cover unique, specific issues or avenues of research concerning sex, and each individual chapter proved engaging enough on its own, but when I arrived at the end of the book I found myself a bit lost; Roach seemed unable to pull it all together into an overarching statement or map about the science of sex, and I found myself wishing that she would broaden her scope a bit.