Richard Perry / The New York Times / Redux A copy of "Fifty Shades of Grey" by E. L. James at the Watchung Booksellers shop in Montclair, New Jersey, March 9, 2012.

Related Bestselling "Mommy Porn" LA Times

We’re under threat again from American women’s rampaging libidos! You may have heard something recently about 50 Shades of Grey, an underground romance novel that has grown women in a hot flash. Annointed “mommy porn” in some circles, its popularity—and the fact that adult women have sexual fantasies—seems be taking people by surprise. Is anyone else getting bored with this theme?

50 Shades has already sold out of its small first printing and just nabbed a publication run of 750,000 books from Vintage Books. Movie rights are under discussion, and national media outlets have featured breathless stories, including on the front page of the New York Times, of the “phenomemon” of adult women (invariably dismissed as “suburban moms”) furtively embracing soft porn erotica with some S & M flavor.

Told from the perspective of a girlish innocent, the Seattle-based story features an emotionally tortured, hyper-controlling boyfriend who can’t get a grip on his baser instincts. If this sounds suspiciously like Twilight, you’re right: it started out as a piece of Twilight fan-fiction by E.L James and the story strenuously echoes the tone and plot of the blockbuster Stephenie Meyer series. But this time around, things are a bit more reality-based; the hot guy is a sexual dominant, his innocent co-ed a reluctant submissive. And the sex scenes don’t fade to black.

(MORE: Erika Christakis on The Harsh Bigotry of Twilight-Haters)

But for all the excitement, the story hardly qualifies as pornography by today’s standards, and it contains a subtle but moralizing undercurrent: the wealthy “Mr. Grey” comes with a steamer trunk of self-loathing and seems just a few more spankings away from being redeemed by his not-so-submissive pet. (All in good time, of course; this is part one of a trilogy.) You know you’re in Girl Land when the sex scenes are interspersed with pages of angsty email exchanges about where the relationship is headed. (Oh, and the guy is turned on by watching her eat.)

The buzz about this book seems to be that women, apparently, have unregulated fantasy lives. Big deal. Women have been reading erotic fiction for eons. Is there something “phenomenal” about women enjoying sex, or just the possibility of it? Today’s cultural narrative about female sexuality has no shades of grey: young women are being portrayed as louche sluts who need government interventions to control their badly behaving bodies yet, by age 40, turn into spayed harpies with libidos in the dumpster who would happily sacrifice their sex drives for a man who does laundry.

(MORE: Erika Christakis: Men Have Sex Too)

A few facts might be welcome. A 2006 study at McGill University found that women watching sexual imagery reach physical arousal as quickly as men and are sexually aroused by a greater range of images than men. In a landmark 2007 study in the New England Journal of Medicine, researchers found that women remain interested in sex well into their ninth decade. In fact, among women with an intimate partner or spouse, fully 75 percent of women between age 75 and 85 reported sexual desire (compared to 80 percent of men.) Among respondents who had been sexually inactive for at least three months, the major reason given for lack of sex was the male partner’s physical health.

But we still act shocked that women have grown-up desires. After decades of advocacy and progress, it’s hard to believe the staying power of some of these one-dimensional portraits of women. The hype around 50 Shades of Grey feels more like 50 shades of condescension.

MORE: Joel Stein on Body Politics