"The Birth of the Pill" is surely no aphrodisiac, but if you have a libido and any sense of gratitude, you might be provoked by this book to celebrate tonight your quite-new ability to enjoy sex without anxiety — or at least without fear of pregnancy.

Once, men and women fought over sex not because of headaches or monthly blues but because women were sick and tired of pregnancy, child after child after child. "For as long as men and women have been making babies," author Jonathan Eig reminds us, "they've also been trying not to," thrusting all manner of disgusting things inside a woman, threatening her life.

Youngsters will not remember the birth of the Pill, but I do. For millions of women across the globe, and for many of their partners, its widespread availability by the late 1960s instantly changed their todays and tomorrows for the better.

In his previous biographies, Eig has detailed the significant lives of gangster Al Capone and ballplayers Jackie Robinson and Lou Gehrig. This time he introduces us to the unlikely quartet whose passions — in and out of bed — gave us the Pill.

First, Margaret Sanger, perhaps the only name most people can associate with birth control in the United States. Unconventional and controversial, she founded Planned Parenthood with the aim of liberating women to have what Eig describes as "sex, the more the better. Sex without marriage. Sex without children. Sex redesigned, re-engineered, made safe, made limitless, for the pleasure of women." In the end, she would have to step off the stage to let more conservative, cooler psyches win the public relations battles.

Sanger's friendship with Katharine McCormick was key, however. McCormick was the early widow of an International Harvester heir who, schizophrenic, could not give her the married life she hoped for. She would be the key financial patron for private research efforts into hormonal ways to prevent pregnancy.

Those research efforts were led by Gregory "Goody" Pincus, once fired by Harvard and determined to redeem himself. He took on, for public relations' sake, the telegenic and proudly Catholic obstetrician/gynecologist John Rock. A mission once built about the joy of sex, Eig writes, was thus built upon "respectable themes such as population control and sound parenthood." If this were baseball, Rock would be the coach who cheered on the athlete who hit a game-winning run.

Eig writes clearly, engagingly and endearingly, even of the complex science and tangled research involved. But mostly he vividly reminds us that real people suffered for cheap, easy contraception, and that real people made it happen — not so long ago.

Susan Ager, a former columnist for the Detroit Free Press, is at susan@susanager.com