New York ? There’s a juicy tidbit about actress Joan Collins. But Molly Jong-Fast, daughter of “Fear of Flying” author Erica Jong, says some secrets from her colorful family have been spared in her new memoir.

“I try not to scoop my mother in my writing — especially about her life,” the 26-year-old says during a recent interview at her apartment on Manhattan’s Upper East Side.

Nonetheless, her mother’s ex-boyfriends — from the wine dealer who went to jail to the guy who wound up selling vacuum-packed frozen meat from a truck — are fair game in “The Sex Doctors in the Basement: True Stories From a Semi-Celebrity Childhood.”

It’s a tale of growing up amid New York’s wealthy and famous, a tale of nannies, secretaries, potential stepdads and eccentric relatives — including Jong-Fast’s grandfather, novelist Howard Fast, a one-time Communist with a 1,100-page FBI file. In fact, she decided to share her stories with the world not long after 83-year-old Fast married his much younger secretary.

“I thought … this is the time to write about these people because they are so nuts,” said the young author, dressed in jeans, a black shirt and fuzzy light blue slippers, her long, wavy blond hair hanging loose.

Jong-Fast’s tone is irreverent, and she doesn’t shy away from such things as her grandfather’s obsession with his reviews in The New York Times or how her grandmother’s stomach “looked like a tushy placed slightly higher up on the wrong side of her body.”

She has no mercy for Collins, a pal of her mom’s who once told Jong-Fast that she was “too fat” to go on fashion designer Valentino’s yacht. “Even at the tender age of thirteen, I knew that I’d be dining out on this faux pas for the next decade,” she writes.

Jong-Fast gets her revenge by recounting another episode involving the “Dynasty” star. She writes that she opened a mysterious white box that Collins had asked her to drop off — even though it had taped sides and was tied with string.

“I found a wig in Joan Collins’s box, and that’s when I realized that Joan Collins was not all she’s cracked up to be,” she writes.

The not-so-subtle implication — since toned down in the book — resulted in a letter from Collins’ lawyer. A lawyer for Random House then went through the manuscript and took out anything that seemed potentially libelous. To avoid other legal complications, Jong-Fast changed names, often using funny pseudonyms — “Hitler” for a therapist, “Belle” for her grandfather’s second wife, “Mr. Pig” for one of mother’s boyfriends.

Jong-Fast belongs to an elite group: sons and daughters of successful writers who have tried their own hands at the trade. Among them are Susan Cheever, daughter of novelist John Cheever, and Christopher Rice, Ann Rice’s son. Jong-Fast considers Cheever, the author of four family memoirs, a mentor.

“There’s a club of us,” said Cheever, citing Linda Sexton, daughter of Ann Sexton, and Saul Bellow’s son, Adam, among others. Cheever, who changed her name when she got married at age 23 but later took back her father’s name, has published four memoirs, including “Home Before Dark” (1984) about her father.

“It’s very, very difficult,” she said. “There are also great, great gifts to having a brilliant person as a parent. But as Molly’s book so brilliantly describes, it’s very difficult. And she makes it so funny. Which is really the way to go.”

In the introduction to “Sex Doctors,” Jong-Fast says she wrote the book in part to answer the question posed to her over the years by a British journalist and others: “So what’s it like being the daughter of the Queen of Erotica?”

Jong-Fast says it’s “a little bit irritating.” However, “You kind of get used to what your parents are, and you can’t imagine them as anything else.”

She says she wanted to be a writer because she wanted her family to take her seriously. She published her first book, the quasi-autobiographical novel “Normal Girl,” when she was 21 to mixed reviews (she thinks it was “just awful”). Since then, she has completed a Masters of Fine Arts program at Bennington College, married and become a mother.

“Mostly I’ve learned how to do what I’m good at, and not what I’m not good at,” she says of her writing.