“I know nothing about art. But I know what I like, at least that was what I thought when I started this book,” explains Nigel Cawthorne in the introduction to Sex Lives of the Great Artists. “Then I discovered that art was principally about sex.” Compare this revelation to the one that begins Sex Lives of the Great Composers.“I admit it. I was a philistine. I never really listened to classical music until I started writing this book,” he writes. “Now, though, I listen to classical music while I work. Why the transformation? Now that I have studied the lives and loves of the great masters, I understand where they are coming from. Music is sex, bottled.”

Art is sex. Music is sex. Cawthorne has uncovered variations on the same shocking truth in volumes on the popes, the kings and queens of England, and the great dictators. The Vatican exists to enrich the sex life of the figurehead, and the same goes for the British monarchy. Dictators oppress their subjects and invade their neighbors to get laid more often. These arguments are so patently reductive, and he overstates his case to such extremes, that there must be something else going on here. Why read Nigel Cawthorne? I am assuming that you are not a thirteen-year-old boy. (If you are one, and you happen to be ashamed that Debussy’s Afternoon of a Faun moves you to tears, and you are caught with Cawthorne’s book on music, it’s ever-so-slightly possible that this incriminating information will be obscured by the fact that the title of his chapter on the composer rhymes his name with a slang term for a female body part.)

These books unwittingly succeed as parodies of the best-selling biographies that promise psychological insight while actually dishing the dirt.As readers, we may or may not care about John Adams’s role in the Second Continental Congress, but we sure want to know what Abigail was like in the sack. Put it another way: If the biography table at Barnes & Noble were a no-sex zone, you can bet we’d be less likely to pick up a book about Cary Grant, Rudolf Nureyev, or Gertrude Stein. Even more broadly, Cawthorne subverts the very idea of history by bringing it down to the level of gossip, or by implying that it’s always been down there, no matter what we tell ourselves.

You’ve got to appreciate the tension between an extremely wide field of study and an extremely narrow interpretive method. Cawthorne might think with his dick, but his dick has a high I.Q. (for a dick) and a well-rounded liberal education. He delves into the same...