"When you write about sex," says Erica Jong, as she methodically reduces her fingernails to mere shards of their former selves, "you push all kinds of crazy buttons." She, of course, should know. The comment comes as she recalls the brouhaha that surrounded the publication of her first and most successful novel, "Fear of Flying," which she describes, with a surprisingly straight face, as "a first novel about a Barnard girl who wanted to be a writer."

"Fear of Flying" was also a first novel about a Barnard girl who wanted a zipless . . . well, you remember, and since it was the '70s, everyone spent a good deal of time either adoring or vilifying the novel's explicit sexual episodes and the confessional modus operandi of the author.

All manner of self-appointed critics got into the act -- the typesetter who wouldn't set the manuscript in type because he thought it was obscene, the TV network that wouldn't accept ads for the paperback publication, the Smithsonian officials who canceled her speech there for fear she would read something scandalous from the book, the outraged husband who threw his wife's copy across the room, only, she says, to later recant and admit that "it was the most important book he had read in his life."

Her new novel, "Fanny: Being the True History of the Adventures of Fanny Hackabout-Jones," is safely set in the 18th century and so is unlikely to occasion the same sort of controversy. But she still seems to savor the image she had then of sexual adventuress, out there on the erotic frontier, letting out a war whoop as she gave chase to the prudes in their chastely covered wagons.

"Fear of Flying" prepared the way," she says. "In part, it created a new level of sexual awareness. When it first came out, people were saying, oh, come on, women don't have sexual fantasies, and I would get outraged interrogators asking questions, like 'But if women work, who will take care of the children?'" Perils to Pillows

The Pilgrim's progress: She is married again and a mother now, no longer a wanderer in the dark libidinous woods. She has found safe harbor from the dangers and strange creatures that lurked therein, the baleful bisexuals, the insidious psychiatrists, and all the other perils on the path to the liberated self. Now 38, Erica Jong lives with her 32-year-old husband Jon and daughter Molly in a high-ceilinged home in Weston, Conn., back in the bosom of the bourgeosisie.

She doesn't even look the way she did in the posters and pictures that accompanied the avalanche of publicity surrounding "Fear and Flying" and which paper the walls of her study -- the blonde hair flowing long and thick, the head tilted back under the weight of the twinkling eyes and the delighted wide-mouthed smile. Instead, as she settles herself among the pillows and the shadows in a corner of the room, her blue eyes look alarmed behind the smokey oversized glasses, and she appears solid and suburban, slow to laughter -- the blithe spirit turned literary burgher. A No-Roper

Her new novel, "Fanny," she says "shatters the archetype of the masochistic, suicidal woman who reaches out for independece and is punished with death." So much of women's literature, according to Jong, is "overwhelmingly depressive, a lot of what a friend calls '10-ropers' -- they make you want to hang yourself 10 times over." Her own book is about courage, she says, about "how women can be survivors, can be heroic. Not a cartoon figure, not Wonder Woman but someone who doesn't give in to macochism."

The book is written in a prose style somewhat comparable to that of the 18th century and is intended, Jong says, to be a kind of "female picaresque" based loosely on the question of what it would have been like if Tom Jones had been a woman. The heroine, a beautiful orphan raised on a great English country estate, leaves her childhood home under distressing circumstances and wends-her tumultuous way to London and beyond, losing among other things, her virginity, her horse, and her manuscript while becoming, enroute, an initiated witch, a highwaywoman, a whore, a pirate, a mother and an author. "I decided she must be ravished and ravished," Jong says, "because that fits in with the historical spoof on the period." Wing, Wong and Jonathan

"Fanny's" benign reviews must have come in welcome contrast to the ones that greeted Jong's second novel. "'How To Save Your Own Life' got the 'A' treatment for a second novel that was a huge success," she says somewhat starchily. "It was dismissed and attacked and I was subjected to venomous character assassination." The novel, she says, "was more appreciated in Europe. There it was considered a fine example of an American novel."

Here, the novel was considered a not-so-hot example of American autobiography. In it, Jong writes about the effects of success on a writer named Isadora Wing who had written an enormously successful first novel about a character called Candida Wong. Wing, Wong, and Jong were all married to a taciturn Chinese-American psychiatrist, whom Jong now describes as "the sort of many you can ride 10 hours in a car with and he wouldn't say a word."

Allan Jong has since remarried, and he too has a daughter now. Someday, says Erica Jong, "they'll meet in school or in summer camp and wonder what it was all about."

Jong married writer Jonathan Fast nearly three years ago in their Weston home. They have, she says, "an open, close relationship." Together they jog and meditate and criticize one another's work, communicating between their two studies by intercom.

They have been together, she says, since they met in front of the Beverly Hills Hotel, where he had come in his green MG to take her to a party being given by his parents and her good friends, writer Howard Fast and his wife Betty.

"He came up to me and said something like, 'Ms. Jong, I presume.' I fell madly in love and so did he and that was it. I knew this was the person I'd been waiting for all my life." It's all in her second novel, as she points out.

Indeed, it is. In the novel, Isadora's new love is 26-year-old Josh Ace, and her reaction to him is right up there on the sexual seismograph: "What a gas, I thought, looking at his warm face, his aquiline nose, his freckles, his furry beard, his rabbit-toothed smile, what a gas to seduce a kid ." Reborn by the Baby

Their daughter, Molly Miranda Jong-Fast, is 2 years old and red-headed. She was born between pages 284 and 285 of "Fanny." Having the baby, Jong says, "transformed" her. "In my 20s and early 30s I didn't think I wanted children," she says. "But by the time I was 34 or 35, I realized that if I didn't have a baby soon, it was going to be a matter of picking up every stray dog in Connecticut."

Her daughter has taught her, she says, "wonderful things about life. You identify with the parents of the world instead of the kids of the world." Of her daughter, she says, "I think we adore her. She's always been approached with great pleasure. I have no doubt she's destined for great things." 'Sex in the Context of Life'

The past seven years since the publication of "Fear of Flying" have seen, says Jong, "huge changes. People think that liberation means the higher the number of people you slept with, the more liberated you are. But the idea of the new chasity is as much of a myth as the sexual revolution. It's myth and counter-myth. That's what happens when you get your philosophy from magazines. Someone thinks, 'Well, I've slept with 686 men and I'm not satisfied, so now I won't have sex.' Sexual freedom doesn't mean sleeping with everyone you meet, but with people you like a lot."

The "mind and body being integrated, that's true liberation," she continues.

"Sex in the context of life." She herself feels "more liberated now. I don't feel oppressed by all the negative commandments. If I'm monogramous, it's because I want to be, it's not by compulsion." From Condemmed to Contented

Jong has come to a tentative truce with the critical reaction her books tend to arouse, but it doesn't appear to have been easy. "I used to say that my literary reputation was one notch above Xaviera Hollander's," she says. "A lot of critics don't even realize what it is they're reacting against. The male critics were the worst about 'Fear of Flying.' It took me by surprise -- I was a poet, I had a very distinguished reputation at that point. They made it sound as if I were some sort of rabble-rouser, encouraging women to leave their husbands.

"I was outraged at the time," she continues, "but I've learned you can't live for the outer world's notion of you. Either you hang yourself from a beam, or you ignore it. Where is it written that we're supposed to be understood? As long as I have a family and friends who love me and a child and a husband I'm crazy about, why should everyone know who I really am?"

An artist, says Erica Jong, "is self-anointing, self-affirming," and, it seems, somewhat self-appointing as well. "If you're controversial, ahead of your time, you have to learn to expect this sort of criticism," she says. Deep Intentions

There are "about a million different books" that Erica Jong would still like to write. She is at work on what will eventually be an illustrated book on witches, and has ideas for several different novels, including one that would be a mystery or spy story written from the female point of view, and one that would have as a protagonist a woman who was a performer of some sort.

For the record, it might be good to remember that "one's deepest intentions in a novel," according to Jong, are revealed in the plot. "Fanny," she says, "is about a girl who f---- her father and survives. Boy, she says, "was I surprised to find myself writing that."