When the Boston Women’s Health Book Collective published a 75-cent pamphlet in 1971, its message was in sync with the feminist zeitgeist. It was time, the collective declared, for women to take charge of their bodies and their reproduction; no female health concern was to be taboo. The message, delivered when fewer than 10% of doctors in the U.S. were female, helped open up a frank conversation about sexuality, pregnancy, contraception and abortion. In the ensuing 40 years, the female-friendly tome has sold 4 million copies in 25 languages. And even now, when women constitute nearly a third of American doctors, the book shows no sign of slowing down: a ninth edition is coming out in October. Sisterhood is powerful!