A smart new history takes boobs seriously.

3. Everything gives you breast cancer and nothing gives you breast cancer.

Williams learns about all the standard-issue risk factors for what is, by a wide margin, the most common life-threatening cancer among American women: age, family history, obesity, race, early puberty, late menopause. “But—and this is the disconcerting part—most people who get breast cancer have few of these risk factors, other than the big buckets of age and race,” she writes. Ninety percent of women with breast cancer have no known family history of the disease. Just as perplexingly, she notes, “most women with the risk factors, even a bunch of them, still never get breast cancer. In other words, the standard risk factors are fairly useless.”

So basically, if you want to find out your risk for breast cancer, you might as well just duct-tape a stethoscope and a mustache to a Magic 8 Ball and ask him. Don’t forget to flush $30 down the toilet for your copay.

4. Feel yourself up. All the time.

Breast cancer detection, according to Williams, “is as much art as science.” Every woman’s breast tissue is different—some have what are referred to as “denser” breasts, which might be firmer (an aesthetic boon by most standards) but make it more difficult for mammograms to detect abnormalities. And then there’s the issue that mammograms themselves, which use radiation, could actually be dangerous for women who are at the highest risk of breast cancer. (It might sound tempting to hypochondriacally forgo mammograms altogether, but I’d rather let a trustworthy doctor make those decisions.) Breast self-exams, or BSEs, Williams argues, are a vital detection tool—if we can educate women to actually perform them properly, instead of “half-assed shower gropings.”

Williams actually purchases a fake, cancer-ridden practice breast from Amazon.com—and works it over like some sort of tumor-ridden petting zoo (adorable!). But when it comes to her actual human breasts, she discovers, exploration isn’t so straightforward: “It was harder (and painful) to push down very far through all my natural ropy tissue. If I were to develop cancer, I’d have to hope for shallow tumors.” So, OK, it’s not as simple as “feel yourself up,” although the commitment to trying is a valuable step. But BSEs aren’t a pass/fail exam. You don’t get points just for showing up and cupping your boob for 30 seconds. You have to probe systematically and thoroughly for, according to Williams, seven minutes per breast if you want to be sure you’ve covered all the territory. This, obviously, is terrifying. I’m pretty sure I’ve never delved deeply enough into my own breast tissue to detect anything but the most shallow and superficial evils. As far as I know, there’s a fucking balrog down there.

5. Learning about breasts is a feminist action.

Breasts are sexualized, fetishized, criticized, ridiculed, obsessed over, augmented, flaunted, and stigmatized—but rarely are they taken seriously. It's like we think about them constantly while simultaneously not thinking about them at all. I know it's hard for people attracted to breasts to wrap their heads around the idea that they aren't just fun, they're also functional. It's difficult to adjust to the idea that your favorite sexual organs are also reproductive organs. I get it. I know if a baby came out of a penis I'd think of penises way differently (also that baby would be hella gross). But eventually I’d get over it (maybe).

Breasts, writes Williams, need “a safer world more attuned to their vulnerabilities, and they need good listeners, not just good oglers.” Do you hear that, boob men of America? Ogling is not enough. If oglers want to keep on ogling, we're all going to have to start caring more about women's health. I worried a bit going into Breasts that all this feminist advocacy for women's health might make breasts less sexy. (If there’s one thing I’ve learned from being an unapologetic loudmouthed feminist it’s that a lot of people do not like listening to unapologetic loudmouthed feminists.) But thanks to Williams’ indefatigable good humor and conversational candor, I’m inspired to believe that maybe sexy, sexy breasts can help make feminism more sexy! So come on, oglers. It's time to pony up. Next dude who talks to my cleavage instead of my face will be expected to send 20 bucks to Planned Parenthood.

See all the pieces in the new Slate Book Review.