Articles, op-ed pieces and radio shows have been devoted to the sexual practice of "hooking up," but Washington Post reporter Laura Session Stepp's Unhooked is the first book on the phenomenon and, one hopes, not the last. For when someone takes such a volatile aspect of young people's lives and puts it under a microscope -- or in this case, a concerned, disapproving gaze -- you want the large, well-lit view.

Stepp follows three high school girls and six college women through a year in their lives, chronicling their sexual behavior. These girls and women don't date, don't develop long-term relationships or even short, serious ones -- instead, they "hook up." Hooking up, Stepp writes, "isn't exactly anything." It can "consist entirely of one kiss, or it can involve fondling, oral sex, anal sex, intercourse or any combination of those things. It can happen only once with a partner, several times during a week or over many months . . . . It can mean the start of something, the end of something or the whole something." If that sounds as if hooking up can mean almost anything but "fried fish for dinner," Stepp goes on to offer something more definite: What makes hooking up unique is that its practitioners agree that there will be no commitment, no exclusivity, no feelings. The girls adopt the crude talk of crude boys: They speak of hitting it, of boy toys and filler boys, "my plaything" and "my bitch."

Why hook up? According to Stepp, college women, obsessed with academic and career success, say they don't have time for a real relationship; high school girls say lovey-dovey relationships give them the "yucks."

Stepp is troubled: How will these girls learn how to be loving couples in this hook-up culture? Where will they practice the behavior needed to sustain deep and long-term relationships? If they commit to a lack of commitment, how will they ever learn to be intimate? These questions sound reasonable at first, until one remembers that life just doesn't work that way: In our teens and early twenties, sexual relationships are less about intimacy than about expanding our intimate knowledge of people -- a very different thing. Through sex, we discover irrefutable otherness (he dreams of being madly in love; she hates going to sleep alone ), and we are scared and enraptured, frustrated and inspired. We learn less about intimacy in our youthful sex lives than we do about humanity. And of course, there is also lust, something this very unsexy book about sex doesn't take into account. In fact, Unhooked can be downright painful to read. The author resurrects the ugly, old notion of sex as something a female gives in return for a male's good behavior, and she imagines the female body as a thing that can be tarnished by too much use. She advises the girls, "He will seek to win you over only if he thinks you're a prize."And goes on to tell them, "In a smorgasbord of booty, all the hot dishes start looking like they've been on the warming table too long."

It seems strange to have to state the obvious all over again: Both males and females should work hard to gain another's affection and trust. And one's sexuality is not a commodity that, given away too readily and too often, will exhaust or devalue itself. Tell girls that it is such a commodity (as they were told for a number of decades), and they will rebel. The author is conflating what the girls refuse to conflate: love and sexuality. Sometimes they coexist, sometimes not. Loving, faithful marriages in which the sex life has cooled are as much a testament to that fact as a lustful tryst that leads nowhere.

In the final chapter, Stepp writes a letter to mothers and daughters, in which she warns the girls: "Your body is your property. . . . Think about the first home you hope to own. You wouldn't want someone to throw a rock through the front window, would you?" And: "Pornographic is grinding on the dance floor like a dog in heat. It leaves nothing to the imagination." The ugliness of these images seems meant to instill sexual shame.

Stepp is most thought-provoking when she considers the culture at large: All the females she interviews come from reasonably well-off families, we're told, and all are ambitious. "Hooking up enables a young woman to practice a piece of a relationship, the physical, while devoting most of her energy to staying on the honor roll . . . playing lacrosse . . . and applying to graduate programs in engineering."

In a culture that values money and fame above all, that eschews failure, bad luck, trouble and pain, none of us speaks the language of love and forbearance. But it is not hooking up that has created this atmosphere. Hooking up is either a faithful reflection of the culture, a Darwinian response to a world where half the marriages end in divorce, or it is an attempt at something new. Perhaps, this generation, by making sex less precious, less a commodity, will succeed in putting simple humanity back into sex. Why bring someone into your bed? Maybe because she is brilliant and has a whimsical sense of humor, or he is both sarcastic and vulnerable, and has beautiful eyes.

And perhaps as this generation grows up, they will come to relish other sides of an intimate relationship more than we have: the friendship, the shared humor, the familiar and loved body next to you in bed at night. This is the most hopeful outcome of the culture Stepp describes, but no less possible than the outcome she fears -- a generation unable to commit, unable to weather storms or to stomach second place or really to love at all.

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