“The Joy of Sex” is back in a new edition, almost four decades after its steamy debut. We’ll ask what’s changed between the sheets.

Birds do it. Bees do it. Humans do it, and when it’s “on the side” they call it infidelity. But infidelity is understood, practiced and paid for in many different ways around the world. In some countries it’s astonishingly common. In many others it’s not.
In the United States it is, perhaps, to most taboo. Former [...]

Sometimes a novel’s plot is unlikely. Sometimes it’s ripped straight from life — or life we can easily imagine. Novelist Tom Perrotta’s latest book, “The Abstinence Teacher,” is the second type.
Ruth is a broad-minded sex-ed teacher at the local high school — in a suburb where evangelical Christians are taking charge of the local culture. [...]