Little by little over the last few years, “A Year on Earth With Mr. Hell,” a self-published, sex-heavy memoir by an unknown author, has become a word-of-mouth hit among artists and writers.

The novelist and screenwriter Nick Hornby called it “gripping.” The critic Greil Marcus described it as “the most graphically effective sex writing I’ve read in a long time.” Capitalizing on its cult success, the Standard, High Line, a hotel in New York that makes an appearance in its pages, has placed copies in some suites and is selling the book through its website.

The author is Young Kim, who was the romantic partner of the punk rock impresario and provocateur Malcolm McLaren in the last decade of his life. In “A Year on Earth With Mr. Hell,” Ms. Kim, 52, chronicles the first 10 months of her affair with another punk icon, Richard Hell, who recorded his 1977 anthem “Blank Generation” (as Richard Hell and the Voidoids) after putting in time as a member of the influential bands Television and the Heartbreakers.

Mr. Hell, 74, and Mr. McLaren, who died at 64 in 2010, have been inextricably linked in punk lore, and now they share the dedication page — “For Malcolm and Richard” — in Ms. Kim’s book.

“I do think I was a kind of muse to Malcolm,” she said in an interview at the Crosby Hotel in Lower Manhattan. “Richard is my muse.” Though he inspired Ms. Kim to write, Mr. Hell said he does not approve of her book, calling it “revenge porn.”

Ms. Kim met him in 2015, when he presented the Malcolm McLaren Award to the artist Edgar Arceneaux at the Performa biennial in New York. “He emitted a sexiness that literally knocked me off balance,” Ms. Kim writes of Mr. Hell in the book’s introduction, “in spite of the fact that his shirt was unbuttoned practically to his navel — something that normally repulses me. Somehow, he got away with it.”

They saw each other four times after that, rendezvousing at New York locations reflecting their own tastes. For him, the Knickerbocker Bar & Grill; for her, the Standard and Ludlow hotels.

Ms. Kim describes the affair in sentences that are at once clipped and conversational. Detailed descriptions of her outfits take up at least as much space as her accounts of what went on in the bedroom. “I decided I probably think about clothes the way Richard thinks about sex,” Ms. Kim writes.

Bret Easton Ellis, the author of “Less Than Zero” and “American Psycho,” interviewed her on his podcast and said he read the book in a single sitting. “She was really being honest about the sex scenes and what they meant to her,” he said. “There’s an innocence about them that also makes them slightly jolting.”

Ms. Kim, whose parents immigrated from Korea to the United States when she was a baby, grew up on Long Island. She went to Yale and spent a year in law school at New York University before deciding to focus on artistic pursuits.

While studying fashion in Paris in the late 1990s, she met Mr. McLaren at a party for his ex-girlfriend and former colleague in fashion, the designer Vivienne Westwood. Ms. Kim was 26; Mr. McLaren was 52.

“He was my first boyfriend,” she said, adding that their relationship was “romantic right away, and he’s the first man I slept with.”

After Mr. McLaren’s death, Ms. Kim became the executor of his estate.

“Young had been struggling with losing Malcolm and dealing with the estate,” said the creative director Serge Becker, a friend of the couple, who had met Mr. McLaren in the 1980s. “I felt the affair with Richard, however brief and intermittent, had given her a renewed energy.”

Mr. McLaren had a history with the book’s titular subject, having seen Mr. Hell perform (as part of the band Television) in New York in the mid-1970s. Mr. McLaren loved his look — torn T-shirts; safety pins; short, choppy hair — and borrowed it for the designs he created with Ms. Westwood and sold at their London boutique, Sex. That same look became central to the appearance of the band he managed, the Sex Pistols.

Mr. McLaren looms large in Ms. Kim’s book — so much so, that the title is almost misleading. Her narrative bounces between the similarities of Mr. Hell and Mr. McLaren (“He was such a giant child, like Malcolm”) and their differences (“he wasn’t a bon vivant as Malcolm had been”).

At one point, when Mr. Hell tries to pull away from her, she is reminded of the “horrible, sickening feeling” she experienced when Mr. McLaren did the same during their low points.

“A Year on Earth With Mr. Hell” got its start about six months after the beginning of Ms. Kim’s affair with Mr. Hell, when he asked her to “write a few lines about what we’d done together sexually.”

“I’d never written anything dirty in my life, but I was willing to try,” she writes in the introduction. “I sent it, and he loved it, just as I had loved writing it.”

The more she wrote about the affair and what she was going through, the more a book began to take shape. Because her meetings with Mr. Hell were few and far between, her diary entries and correspondence became a large part of the finished product. Though the affair came to an end, Ms. Kim’s portrayal of Mr. Hell is fond.

“Richard, I have to say, elevates sex to an artwork,” she said.

Since his punk rock days, Mr. Hell has focused on his writing, publishing an acclaimed memoir, two novels and collections of essays, criticism and poetry. In an email, he detailed his unfavorable view of Ms. Kim’s book: “How would you feel if you dated someone briefly, including having sex, and it turned out that they were writing about it behind your back and eventually published that misbegotten, uncomprehending — but full of false detail — account of the affair, with a focus on the sex, using your real name?”

Ms. Kim defended her work in an email: “In writing this book I have only done what men have done unapologetically (and I do not think they should apologize) since time immemorial: choose my work over my relationship.” She added that she has kept in mind something the artist Michael Heizer once told her: “Any work of art of any worth (not a Hallmark card) is going to upset someone.”

Mr. Ellis said he saw nothing untoward in Ms. Kim’s depiction of Mr. Hell. “The portrayal of him comes off as very sympathetic and very real,” he said. “There’s an obsessive quality in the way she describes him. He’s a sex god in this.”

Ms. Kim said that she might publish a sequel to “A Year on Earth With Mr. Hell,” as well as a book centered on Mr. McLaren. “They have each given me something really important in my life,” she said. “Malcolm taught me somehow to create, and then Richard gave me the push to do it.”

And how is her love life these days?

“People bring up NDAs,” she said. “It’s come up. At least as a joke.”