Why Is Sex Fun?: The Evolution of Human Sexuality, by Jared Diamond (Phoenix, £5.99 in UK)

Well, it isn't, really - at least, not the way Jared Diamond does it. On the contrary, he sees human sexuality as a very serious business indeed, and this book will tell you things you never even dreamed of asking about conjugal relations not just between humans, but also between such philandering fauna as the Pied Flycatcher and the Dyak Fruit Bat. Diamond's thesis is that unusual sexual habits were as crucial to our rise to human status as the increase in the size of our brains; he argues his case in a lively fashion, but ultimately he doesn't seem to have much in the way of hard evidence.