In 1970, when Jill Ciment was a rebellious teenager, she did something shocking.

Dreaming of becoming an artist, Ciment signed up for classes with Arnold Mesches, a well-known painter whose work she admired. Respect grew into infatuation, and one night after class, she waited for the other students to leave, and approached him.

“I unbuttoned the top three buttons of my peasant blouse, crossed the ink-splattered floor, and kissed him,” Ciment, now an acclaimed novelist, wrote in her 1996 memoir, “Half a Life.”

She was 17 at the time. He was 47, married with two teenage children.

When Ciment wrote “Half a Life,” she and Mesches had been together for more than 20 years. He was the first reader on everything she wrote. After reading the scene, he had quibbled with a few phrases, but agreed on the key fact: She instigated the kiss.

A few years ago, Ciment found herself reconsidering their origin story. Mesches had died of leukemia in 2016, at age 93. The #MeToo movement had unleashed a debate about sexual harassment and assault committed by men in positions of power. Ciment started to question her earlier account of their courtship.

She picked up “Half a Life” and found the passage describing their first kiss. She was stunned by how she had distorted the encounter, she said. She recalled that night perfectly, because she had fantasized about it for months afterward. After the other students left the art studio, she lingered. She wanted to ask Mesches for advice on how to pursue a career as an artist. He pulled her toward him and kissed her.

Looking back on it five decades later, she realized there was something sinister about his conduct that she had failed to grasp before — an older man, a teacher in a position of power, taking advantage of his student, a teenager who craved his approval.

“In a marriage you have this shared mythology, and you have to share the mythology while your partner’s still alive,” Ciment said. “But once your partner dies, the story becomes yours.”

Ciment decided to perform an autopsy on her memoir. The exercise yielded a new memoir, titled “Consent,” which Pantheon will release on Tuesday. With almost clinical detachment, Ciment investigates the flaws and factual lapses in her earlier work, and in doing so, questions the artifice inherent in memoir as a literary form.

“The whole idea of writing truth in a memoir is so preposterous,” Ciment said. “You have these scattered memories, and you’re trying to carve a story out of them.”

Ciment spoke over tea at her home in Gainesville, Fla., which is filled with Mesches’ bold acrylic paintings and is perched on a placid lake where alligators often sun themselves on the shore. Ciment, who has a halo of gray curls, hazel eyes and a low, quick laugh that frequently punctuates her sentences, sat in front of a large triptych of oil paintings by Mesches of a horse, a turkey and a sad looking Chihuahua in a hat. “I used to call these his three self-portraits,” Ciment said.

It’s unusual for a writer to revisit past work, and take it apart in such a public fashion. “Consent” is a surprising and often jarring book: part memoir and postmortem, part recrimination and reclamation, and yet, part love story, too.

In the first half of the book, Ciment scrutinizes the story she told about her early years with Mesches in “Half a Life.” Sometimes, she reprints whole passages from her earlier memoir, then recounts the same events, disclosing what she distorted or left out. In the second half, she picks up where her first memoir left off, and describes their decades of marriage, the way their creative lives became intertwined, and what it was like to grow older as the younger woman, and to have Mesches become increasingly dependent on her in old age.

Sifting through her own words in “Half a Life,” weighing them against her memories, Ciment was left with an uncomfortable conclusion: She hadn’t told the full truth, maybe because she wasn’t able to.

“I don’t know if I could really write the truth. When what you’re writing is being read by the person that you’re writing about, can you be completely honest?” she said. “I’m sure that his being a part of the writing of the memoir changed the memoir. Once I was free of having that collaborative story, I was free to look at it again.”

Ciment was shocked by other relevant details that she had omitted in “Half a Life.” Even before their first kiss, Mesches made no secret of his interest in her. He would lean over her in class to inspect her work and look down her shirt. Once, during class, he whispered in her ear, “I wish you were older” — which Ciment left out of her first memoir.

Mesches was a serial adulterer who had cycled through a parade of women, including other students. When their affair began, Mesches, who had turned to teaching because his painting career was in a slump, was already cheating on his wife with another woman, but Ciment made no mention of this in “Half a Life.” (She later became friends with that other woman, she said.)

She left out the fact that when she was still a teenager, she and Mesches occasionally had sex in a park near his studio, and they once narrowly escaped being caught by a passing police officer while she was performing oral sex on him. She left out the many meals they had at a Chinese restaurant with a discreet dark booth at the back, where they would often go after having sex in his art studio, and where the waiter knew their drink orders: a Coke for her, a vodka martini for him.

When she wrote about the first time they had sex in “Half a Life,” it was a scene of mutual unbridled passion. Recounting the same night in “Consent,” she reveals new details that make the encounter more ambiguous. She found the sagging skin of his middle-aged neck “repulsive,” but “chose to overlook it.” When they lay down on the soiled sheets of a cot in his art studio, Mesches was unable to get an erection. He suggested that she fellate him, and because she was so inexperienced, he told her exactly what to do.

Now 71, Ciment believes that in “Half a Life” she didn’t set out to protect Mesches from being labeled a predator. Rather, she hadn’t wanted to think of herself as prey.

“Would he have been upset if I had written that he had kissed me? No, he wouldn’t have been,” she said. “I wanted to show my own empowerment, more than to hide from his faults.”

While she was writing “Consent,” Ciment occasionally wondered what Mesches would make of it were he still alive.

“The thing that would trouble him the most,” she said, “is that I wrote about his failures and how he had given up as an artist.”

Some of Ciment’s closest friends were unsurprised that she decided to revisit her first memoir, and essentially tear it down.

“I knew she’d be ruthless and honest,” said Amy Hempel, a short story writer who has been a close friend of Ciment’s for decades. “She makes herself as accountable as he is. She’s no victim.”

Ciment’s life before she met Mesches was marked by chaos and instability. Her father, mentally ill and prone to violent tantrums, grew estranged from the family after her mother kicked him out of their home in Los Angeles. After that, her mother struggled to keep the household afloat and care for four children on her own.

Ciment dropped out of high school to become an artist, and after taking Mesches’ class, she moved to New York to pursue her dream, but instead ended up working as a nude model at a peep show near Times Square. When she returned home after four months, broke and defeated, she went to see Mesches, and they resumed their affair.

He eventually left his wife, and when Ciment was 18, they moved into a small bungalow near a freeway. She was admitted to CalArts, using fake SAT scores that she had gotten by asking a friend to take the test for her. Worried that as an artist she might never emerge from Mesches’ shadow, she eventually gave up art and started writing.

In the early 1980s, they moved to New York and lived in a fourth-floor walk-up in the East Village. At the end of the day, they showed each other their work, and were often brutally honest in their critiques.

“They were true equals, and you don’t see that often in any relationship, let alone a relationship where one of them is 30 years older than the other,” said the writer Jo Ann Beard, a close friend of Ciment’s.

Still, Beard said she understood why Ciment had failed to tell the full story of their relationship in “Half a Life.”

“She made an effort to protect him from the world’s judgment, and by the way, it also protected her from the world’s judgment,” she said.

Ciment was 40 by the time she published her first novel, “The Law of Falling Bodies,” which was heavily autobiographical, and centered on a teenage girl from an unstable home who falls in love with a man named Arthur who is 30 years her senior.

Some of her later novels also contain fictional portraits of their marriage. Her 2009 novel “Heroic Measures” features an older couple living in a walk-up in the East Village; like Mesches, the husband in the novel is an aging artist whose paintings incorporate pages of a dossier that the F.B.I. compiled about him during the Cold War. (Ciment wrote it after Mesches had already turned his own dossier into a series of paintings, “The F.B.I. Files.”)

In her 2019 novel “The Body in Question,” Ciment drew on her experience of being Mesches’ caretaker in his final years. The novel centers on a 52-year-old Florida woman named Hannah, who is relieved to get a break from caring for her infirm 86-year-old husband when she is selected as a juror for a sensational murder trial.

Ciment started writing it when Mesches was 91, and gave the fictional husband an acute form of leukemia, the same disease that eventually killed Mesches. She repurposed some of their conversations about his impending death as dialogue between the novel’s husband and wife, and some of the lines from the novel appear verbatim in “Consent.”

“One of the things I wrote into that novel was his death, so that when he died I would have a place to put my grief,” Ciment said.

Now that she’s done with “Consent,” Ciment is imagining how she might rewrite the book if she revisits it decades from now.

“When I hit 90, if I should feel the urge to, I would probably rewrite these pages to talk about how Arnold taught me how to age,” she said.

“He never gave up,” she continued. “He went into that studio a week before his death and he drew and he painted. I learned something invaluable, which is that you’re alive as long as you’re alive.”