WHEN PEOPLE hear I am writing a book about how a woman ages, they're always ready with the punchline: "Badly." An aging woman is a joke, a bundle of bags, sags, and wrinkles that place her in the easily-dismissed category of "not I." Yet those of us who are women will, if we are lucky, become old women. Will we then think of ourselves as jokes--or, worse, as creatures to be pitied, condescended to, and ignored?

Elissa Melamed began examining this question when she turned 40. "I was feeling divided, divided against myself," writes Melamed, a psychotherapist who was living in New Mexico at the time: "a changeless person trapped inside a changing body; a centered person at odds with a needy person; an honest person ashamed of the 'me' who wanted to play the youth game." Melamed organized a support group for other women her age, and she was startled to find that the others shared her feelings. "It was clear to me," she writes, "that women have a 'social fixation' on youth and young adulthood which prevents their full maturation into the second half of their lives. This fixation is of such epidemic proportions that we accept it as normal."

But it is not normal, Melamed maintains. It goes against everything that is normal. Women past their "prime"--the age of childbearing, usually the twenties and early thirties--are considered useless goods. They fight obsolesence with a vengeance, slathering $6 million of skin cream on their faces every day (Melamed calls it "buying youth") and single-handedly supporting the nation's plastic surgeons, who depend on unmarried, divorced, or widowed women over 40 for three-quarters of their trade. But despite the money devoted to conquering flab and vanquishing wrinkles, old women still look like old women. And there's no place for old women to go.

Mirror Mirror is an interesting exploration of a fascinating topic. Why is "not being young" so much more terrifying for women than for men? Why is an older man allowed to be distinguished, charming, debonair, powerful, successful, even lusty, while an older woman is at best "gracious" or--that most neutered of all compliments--"handsome"? Why does an older man retain, and sometimes increase, his sex appeal with age and power, while an older woman, upon turning 50 or so, becomes a sexless matron? Why do most men accept their aging with good will and equanimity, while most women view the gray hairs and wrinkles as death knells for their self esteem?

A woman's individual terror at approaching age is at its core a social disease. Western society has turned old age--especially female old age--into a debility, and women respond by acting debilitated. They try to cover up the outward signs of aging with rouge, hair dye, and face lifts. But they have internalized the message, and that is a damage they cannot hide.

Because older women are continually reminded that they are second class, Melamed says, they develop psychological problems that keep them second class--particularly agoraphobia (a fear of public places that turns its victims into prisoners in their own homes), depression, eating disorders, alcoholism, and drug abuse. They exaggerate the physical discomforts of aging and the menopause, and rely heavily on physicians who are all-too-willing to cut out their reproductive organs or dope them up with estrogens and Valium. The "terror of not being young" creates a vicious circle--an elderly woman is defined as useless, and a useless woman begins to act more and more elderly and more and more useless.

Mirror Mirror says in 220 pages what probably could have been said in 20. But it is an interesting topic and one worthy of inquiry. Melamed is a skilled writer and a careful thinker, and wears her feminism proudly without being strident about it. She examines many familiar topics--media images of older women, plastic surgery, the fear of aging--in an interesting way, and explores some topics that are not so familiar--especially that of "appearance anxiety," the female equivalent of men's "performance anxiety," and of "neutering," the stripping away of sexuality which she says occurs to most older women.

Melamed attempts to give an international flavor to Mirror Mirror by including quotes from the 200 women she interviewed from seven countries--Belgium, England, France, Ireland, Italy, Switzerland, and the United States. But this technique does not quite work. While it no doubt made a lovely sojourn for her, it wasn't really necessary, in terms of strengthening the book, for her to do her research "(drinking) tea in Irish kitchens and champagne in Louis XV drawing rooms." As she herself says, the particular problem of aging women is not unique to Americans: "It goes with urban living and the breakdown of traditional life styles more than with nationality. A Parisian secretary will be more concerned about aging than will a Minnesota farm wife." Melamed would have had an international statement to make, therefore, just by interviewing a cross section of Americans.

In any event, many of the quotes from interviewees are affecting (although Melamed too often neglects to give women's ages). Consider this vignette from a 45- year-old woman, at a luncheon meeting with a former lover she has not seen for 15 years. "I was a little nervous," she recalls. "Suddenly I noticed him staring at my hand on the table. I looked down and suddenly saw it through his eyes. And it was a 45-year-old hand. . . At that moment I felt a surge of hate for my hands--the wrinkles, the veins, the age spots--and I hated him for making me feel that way and I hated myself too." The self- loathing echoed in this woman's words, as in the words of many of the women quoted here, is perhaps the most haunting aspect of this book. And we must do something about it quickly. Vast human resources lie untapped in the 35 million American women over age 45--the fastest-growing segment of the population--and we cannot continue to squander them in this way.