First let me say I snapped up this book with a burning hunger to save my 7-year-old granddaughter from becoming an inevitable teenaged slut.

Its painfully provocative cover photo and the words on its jacket promise it is about "the physical, emotional, and social milestones of every girl's life: what we've lost and gained in the 21st century."

Gained? Girls are no longer sheltered and shy. Girls can work at any job they wish. And, um ... what else, then?

But I must also say that Caitlin Flanagan's "Girl Land" (Little Brown, 224 pages, $25.99) did not calm me or teach me anything about how to save Katie. It is a rant much like my own by a woman who, it turns out, is the mother of two sons.

Aha! No wonder so much of her storytelling is about her own Girl Land -- the time and place in which a girl works out how to become a woman, "an act partly of nature and partly of self-invention." In Girl Land (the space where girls tend to spend time alone in their rooms or giggling with friends), a girl is "coming to terms with her emergence as a sexual creature," and all the joys and terrors that includes, along with "mourning the loss of her little girlhood."

It is a time "drenched in romance," in a culture with "driving imperatives of exhibitionism."

Every grandma and most mothers and aunts know all this. We've heard about prom nights, and oral sex, and we cringe to open the Facebook pages of our beloved adolescent girls, and we try not to gasp at what they wear.

But this book is of no help to us. It is sporadically interesting, flipping through history, spotlighting Patty Hearst and Judy Blume and Seventeen magazine alike. It reads, though, as if Flanagan is writing therapeutically. She dwells long and often on an episode when she was 16 when a boy she hardly knew got fresh with her in a car. (Um, isn't that a universal rite of passage?)

She has titled her chapters "Dating," "Menstruation," "Diaries," "Sexual Initiation," "Proms" and "Moral Panics" (as in the latest one linked to reports of 24/7 oral sex between needy boys and indifferent girls). Her advice is simplistic: Go with the flow, or fight the culture. To help decide, "take the 15-minute tour" by typing "porn" into your search box. Then keep computers out of her room, make sure a "powerful adult male" figure stands tall over her dates, don't be afraid to set limits and remember she'll eventually grow up.

Read "Girl Land" to reminisce about your own dates, proms, periods and panics -- but not to learn how to save the sweet young girls you love.

Susan Ager is at susanager.com.