If you can transplant a face, then why not a penis? Why doesn't Viagra help women or, for that matter, pandas? Does an orgasm boost fertility? Cure hiccups? Do the earlobes swell during sex? 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? 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 has devoted the past two years to stepping behind those doors. The result is Bonk - everything you wanted to know about sex but couldn't imagine that someone in a white lab coat had studied. Few things are as fundamental to human happiness as satisfying sex. 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.