The study of sexual physiology-what happens, and why, and how to make it happen better-has been a paying career or a diverting sideline for scientists as far-ranging as Leonardo da Vinci, James Watson and Napoleon Bonaparte's great grand-niece Marie. The research has taken place behind the closed doors of laboratories, brothels, MRI centres, pig farms, sex toy R&D labs and Alfred Kinsey's attic. Mary Roach devoted the past two years to stepping behind those doors. The result is Bonk: everything you wanted to know but couldn't imagine that someone in a white lab coat had studied. Can a person think herself to orgasm? Can a dead man get an erection? Can Kegeling cure erectile dysfunction? Can Broadway musicals cause it? Is vaginal orgasm a myth? If you can transplant a face, then why not a penis? What happens if you surgically relocate your clitoris? Why doesn't Viagra help women-or, for that matter, pandas? Does orgasm boost fertility? Cure hiccups? Do the earlobes swell during sex? Few things are as fundamental to human happiness than satisfying sex. Yet the funding for research, always elusive, has dwindled sharply. Bonk is both an ode to a fascinating and vital pursuit and a reminder that there is still much to learn. Sexual arousal and orgasm are two of the most complex, delightful, utterly amazing scientific phenomena on earth. Sexology, as Roach approaches it, is right up there too.