Nancy Friday in the mid-1990s. Her 1973 debut, “My Secret Garden,” sold more than 2 million copies. (Bob Berg/Getty Images)

Nancy Friday, a dissatisfied daughter of the sexual revolution whose best-selling books aimed to liberate women from embarrassment over their erotic fantasies and from fraught relationships with their mothers, died Nov. 5 at her home in Manhattan. She was 84.

The cause was complications from Alzheimer’s disease, said her friend Eric Krebs, who produced an off-Broadway theatrical adaptation of her 1973 debut, “My Secret Garden.

Ms. Friday was living in London, penning sex and courtship columns for Cosmopolitan magazine, when she decided to follow in the footsteps of writers such as David Reuben and the pseudonymous “J.,” whose 1969 sex manuals “Everything You Always Wanted to Know About Sex (But Were Afraid to Ask)” and “The Sensuous Woman” had become nightstand staples for millions of Americans.

Placing an anonymous advertisement in newspapers and magazines, she received hundreds of letters and conducted scores of interviews that formed the basis of “My Secret Garden,” a survey of female sexual fantasies that aimed to show women that there was nothing shameful or embarrassing about such daydreams — and to show men that women’s sexual imaginations existed.

“I’ve always suspected that women have richer, wilder fantasies than men,” novelist Henry Miller wrote in an assessment of the book, which featured chapters such as “The Sexuality of Terror, or, ‘Help, I’m Out of Control, Thank God!’ ” The fantasies Ms. Friday cited ranged from violent rape dreams and visions of bestiality (too many, psychologists and sex therapists said) to imaginative chronicles of “group gropes” and adventures with vacuum-cleaner nozzles.

The book sold more than 2 million copies and established Ms. Friday “as the liberator of the female libido,” Newsday wrote, and a frequent talk-show guest.

She developed as indelible an association with sexual fantasies as sex educator Betty Dodson was with masturbation, writing follow-up works of pop psychology that included “Forbidden Flowers” (1975); “Men in Love” (1980) about male fantasies; and the volumes “Women on Top” (1991) and “Beyond My Control” (2009), which charted the daydreams of younger generations.

But she also branched into new issues of gender and sexuality with “My Mother/My Self” (1977), a semi-autobiographical work in which she argued that women inherit many of their anxieties and insecurities from their mothers; “Jealousy” (1985), a study of the emotion; and “The Power of Beauty” (1996), which implored women to acknowledge the sway that looks can hold in their relationships.

Although the reception to her work slipped over the years — “Rigorous thought is obviously not her strength,” the New York Times arts critic Caryn James wrote in a review of “Beauty” — Ms. Friday maintained a reputation as a lively force of sexual liberation for decades, living by the motto “more sauce and bigger drinks.”

She split her time between apartments in Key West, Fla., and New York, browsed the Sotheby Parke-Bernet auction house whenever she found herself with writer’s block and flaunted the birth-control pill that she carried inside a gold bracelet.

Yet she also maintained a strained relationship with women’s movement leaders such as Gloria Steinem, whose publication Ms. magazine excoriated Ms. Friday in a review of “My Secret Garden.” “This woman is not a feminist,” the reviewer wrote, joining a group of critics who argued that Ms. Friday focused on women’s sexual growth at the expense of their political or economic advancement.

Ms. Friday, in turn, lamented what she described as “anti-men, anti-sex matriarchal feminists,” insisting that her work was addressing far more than fantasies or daydreams.

“After I wrote ‘My Secret Garden,’ ” she told People magazine in 1980, “I began getting letters from women expressing gratitude. ‘Thank God you wrote that book,’ they said. ‘I thought I was the only one.’ Your sexual fantasies are one of the most valuable X-rays you’ll ever have.”

Nancy Colbert Friday was born to a teenage mother in Pittsburgh on Aug. 27, 1933. Her parents divorced when she was a child, and Nancy was raised in part by her grandfather, a steel tycoon, in Charleston, S.C. “There is nothing like the mystery of an absent father to addict you to the loving gaze of men,” she later wrote.

Ms. Friday graduated from Wellesley College in 1955 and worked as a reporter in Puerto Rico, where her work drew the attention of publisher Michael Butler. Butler, who later produced the countercultural Broadway musical “Hair,” gave Ms. Friday a position as the editor of a travel magazine. She described him as her “sexual emancipator” and eventually she moved to New York, searching for a job that would give her the “freedom to pursue men at a moment’s notice.”

She did public-relations work and in 1967 married Bill Manville, a novelist and Village Voice columnist. The couple moved to Europe, where Ms. Friday began work on “My Secret Garden.” The marriage ended in divorce; according to a 1995 story in Esquire, it fractured over the question of the authorship of Ms. Friday’s books, with Manville eventually acknowledging that Ms. Friday was their sole author.

A marriage to then-Wall Street Journal Managing Editor Norman Pearlstine in 1988, at a star-studded wedding that included future president Donald Trump and investor Ronald Perelman, also ended in divorce.

Ms. Friday had no children and leaves no immediate survivors. “I couldn’t write the books I have if I were a mother,” she told Newsday in 1991. “Then ‘Good Nancy’ would be in charge. The one who’s less comfortable talking about sex.”