Participatory journalist Mary Roach has made a tidy career for herself from breezy pop-science books with one-syllable titles: Stiff (what happens to cadavers?) and Spook (how do you investigate the afterlife?). But with her latest work, Bonk: The Curious Coupling Of Science And Sex, Roach might just have found the book she was born to write. Her fearless (or is that shameless?) style perfectly suits this exploration of sex in the laboratory, both historical and contemporary. From Kinsey to Viagra to coitus in an MRI machine, Bonk reveals with incessant good humor how little we know about our basic reproductive drive, and how difficult it is to design experiments to find out what we might want to know.

For example, one area of scientific ignorance is the chemistry of female ejaculate. Various researchers have reported that it's identical to urine, or that it has compounds related to semen, or that it doesn't exist at all. When one considers the difficulty of collecting and isolating the fluid, it ceases to be surprising that we remain in the dark. And the same goes for the nature of the female orgasm (clitoral? vaginal? multiple?) and the relative importance of the brain, as opposed to simple reflexes, in arousal and climax. When possible, Roach observes researchers doing ghastly penis surgery or quantifying bonobo mating behavior or manufacturing artificial vaginas. But when privacy is an issue, the author gamely inserts probes while watching pornography, and even enlists her husband to have very scientific intercourse with her while being recorded ultrasonically.

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Bonk obviously isn't for the prudish, but it also isn't for the squeamish. (Those who feel light-headed at the thought of objects being inserted into the male urethra are advised to read in a reclining position.) Its one minor fault is a tendency to downplay chronology in favor of a good yarn; Roach prefers to hook her history onto firsthand contemporary narrative, so Masters and Johnson, along with other sex-research classics, tend to pop up whenever they're needed. But her humorous, frank style—frequently digressing to hilarious effect in the footnotes—seems to have matured completely in her third outing. Perhaps that's because sex and science are both poignant efforts to attach meaning to fundamental human desires. (There's a reason there's a Biblical connotation of the verb "to know.") Laughter is a perfectly appropriate response to both.