In the gray days of the '50s, Rona Jaffe was haunted by Marjorie Morningstar.

"I would tell my dates about how I wanted to be a writer and they would laugh and say, 'Oh, sure, just like Marjorie Morningstar - you'll marry me and live in the subursb,'" she said yesterday. "And all the women I knew actually married men like that."

Not Rona Jaffe. She didn't get married, she lives in midtown Manhattan and she has written about men like that in her latest book, "Class Reunion" - her tenth book, and her fifth bestseller.

The book follows the trials and tribulations of eight members of the Class of '57 of Harvard and Radcliffe as they try to crawl out from under the mind-numbing conformity of the '50s. Jaffe should know. She went through it all, Class of '51, and in some ways, it is with her still, waiting to be exorcised.

The claustrophobia of those days comes back to her easily as she sits and reminisces in the Madison Hotel, in the middle of a 20-city book tour. "Everything was rules," she says."It's amazing now to look back and see how no one ever questioned any of them. There we were reading poetry and writing sonnets and all the while trying as hard as we could to get married. It was a real race - if you were the first to be married and have a child, your baby was the class mascot and you got a set of Radcliffe china."

And while Jaffe broke the rule about marriage - "I didn't want any of the ones who asked me and the ones I asked said no" - the careful adherence to the prevailing cultural trade-winds has continued.

"I always have done what everyone else was doing," she says with not one mea culpa in the direction that the ersatz individuality of the last decade would demand.

"In the 60s I straightened my hair, wore lots of eye makeup and lived in a big apartment on the West Side and stayed up all night carrying on," she says, eyebrows arched by the ludricrous light in which such activities are now perceived. "I was looking for the thrilling experience."

Now she is dressed softly in a gathered cotton skirt and her brown hair is "in a frizzy permament. I have no will power. I'm basically following the general perspective of the Me Decade. I've moved into a smaller apartment. I'm getting my house in order and finding a kind of stability."

Her observations are edged in irony, but like any veteran of a vicious war, past skirmishes are with her still, and she is still in the trenches. She distrusts the sentimentally in which the '50s are currently being emulsified on the sitcoms. What she remembers are the girls without dates checking the ones who had dates on Saturday night for signs of smeared lipstick and the accusations.

"It was painful for the ones who were different - and being Jewish was being different then - and it was painful for the ones trying to conform." And around it all hung the once awesome and now antiquated question of sex, yes or no, if and when, guilt and more guilt. It was the pervasiveness of that question that anchors Jaffe's books and perspective and it is the anachronistic nature of that question which makes the social history of the decade so silly and so sad.

"I remember coming in one night when this girl looked at me very accusingly and said, 'Your blouse is buttoned wrong,'" Jaffe said. "And I just smiled and said, 'It's okay, he loves me.'"

If she had been born a decade later, she says, she would have been able to write about other themes, would not have been so beset with the problems and life styles of the women of her generation. "In college we tried so hard to be perfect," she said. "And then when we got out everyone was in analysis. I spent years trying to figure out why I wasn't married. So did a lot of women. If only the women's lib movement had come along 10 years earlier, we would all have saved a fortuned."

Political catalysts like the feminist and the anti-war movements are not prominent among the factors that account for changes in Jaffe's characters. "People were totally involved in their marriages and nervous breakdowns," she says. "Vietnam didn't cause drinking problems, and women were getting migraines from their marriages before the women's movement came along."

Jaffe says her books take her about two years to write - a year and a half to plan it, sketching the characters, theme and plot in her mind's eye, and six months to do the actual writing. "Class Reunion" was compared by one critic to soap opera, "absorbing and embarrasisng at the same time," but she sees it as social commentary. She also knows her place in the literary pantheon.

"I've never been accepted by the literary establishment," defined as "those people who write reviews for each other's books. God knows I've paid enough dues. But a lot of people in the public know me. People think it's only the intellectual and the rich who read, but it's just not true," and when she is on the road, they come up to her and ask for her autograph and ask for her advice.

Rona Jaffe has been around, around the country and the changing cultural landscape, but one place she hasn't been is her own class reunion.

"They asked for pictures of your husband and your children," she said. "I was afraid no one would talk to me." CAPTION: Picture 1, Author Rona Jaffe, by Vanessa R. Barnes - The Washington Post, Picture 2, Rona Jaffe, by Vanessa Barnes - The Washington Post