Earlier this year, Mary Trump, a niece and prominent critic of Donald J. Trump, had a bad bout of writer’s block. She was juggling several nonfiction projects and felt stuck, so she decided to write something completely different.

The result will surprise readers who know Trump from her blockbuster memoir, “Too Much and Never Enough,” which told the inside story of Donald Trump’s family history. It has nothing to do with the former president, politics or clinical psychology, her professional field. Her latest book, “The Italian Lesson,” is a romance novel about an American woman with a secret past who tries to reinvent herself in Tuscany, where she opens a cafe and meets a handsome local vineyard owner.

“It’s completely unlikely and weird and counterintuitive,” Trump said of the project.

The novel, which will be released on Substack over the next year, with the first installment arriving on Friday, came out of an unusual collaboration between Trump and two of her close friends: E. Jean Carroll, the advice columnist who won a sexual abuse and defamation case against Donald Trump, and Jennifer Taub, the author and law professor.

The three became close during the pandemic, when they all joined a Zoom knitting circle. Later, they decided it would be fun to collaborate on a screenplay for a Hallmark-type romance movie as a way to stay in regular touch.

“We really didn’t want to lose each other,” said Taub, who was knitting during a joint Zoom interview.

The screenplay never got off the ground, but Trump had the idea to write the story as a serialized romance novel instead. Since they all have newsletters with Substack, it seemed like a natural choice for a platform.

Trump, who started out writing fiction before she published her nonfiction best seller, volunteered to write it, but felt she was out of her depth on the romance elements. “I’ve never read a romance novel in my life,” she said.

Carroll, who has frequently dispensed romantic advice through her column, “Ask E. Jean,” helped Trump with tips for writing bedroom scenes and realistic romantic scenarios. (For one thing, Trump had failed to adequately describe the outfit that her heroine, Anastasia, wears on her first date with her love interest, Matteo, a rookie oversight that Carroll and Taub helped her address.)

For the most part, the collaboration has been seamless, though they’ve occasionally clashed over just how spicy the plot should be. During the Zoom interview, Trump and Carroll disagreed about whether the novel could accurately be described as “erotic.”

“This is not soft-core pornography,” Trump said.

“Let’s wait,” Carroll countered.

“I don’t have it in me,” Trump demurred.

“Mary, you do,” Carroll insisted.

Carroll then tried to settle the question: “I think we are going to have some very delicious scenes, as only Mary can describe them, so they’re going to be a little weird, but trust me, there are going to be some erotic scenes.”

One thing they all agree on: There will be no discussion of the former president, or of politics in any form, on their Substack.

“This is a no-politics zone,” Carroll said. “We’re giving you an escape.”

Of course, they realize that many people have come to associate them with political and social commentary — not erotic thrills — and that some readers may be disappointed by their new mission. Both Carroll and Trump gained prominence for taking on the former president in their memoirs, becoming heroes to many on the left and magnets for attacks and criticism from the right.

In her 2019 memoir, “What Do We Need Men For?,” Carroll accused Trump of raping her in a Manhattan department store dressing room in the mid-1990s. She later sued him, and a jury in her civil case recently found him liable for sexual abuse and defamation, and ordered him to pay Carroll $2 million for the sexual abuse and $3 million for the defamation. She is seeking new damages in response to comments he made on CNN after the verdict.

Mary Trump became a cable news fixture and practically a household name in the summer of 2020, when she released a blistering tell-all about her uncle with Simon & Schuster. The book sold more than 1.3 million copies in the first week after its release.

Trump said she had brushed aside concerns from a few people in her professional orbit, who worried that a romance novel might dilute her reputation as a sharp political commentator.

“Some people said we’re tarnishing the brand — what brand?” she said. “I don’t really care what anyone thinks, or if people go, ‘Oh, it’s a romance novel and you’re not a serious person.’”

Trump has written about a third of the novel and has the plot fully mapped out, she said. She hopes to find a traditional publisher for the novel when it’s finished. For now, subscribers to the Substack will get twice-weekly installments, along with knitting patterns and recipes for Italian dishes that the characters eat. (The Substack, called Backstory Serial, will be free for the first three weeks, then available to paid subscribers for $60 a year or $6 a month.)

Subscribers can also leave comments about the story, and Carroll will respond to readers. But trolls will not be tolerated.

“If you want to insult me, if you want to be mean to me, that’s what Twitter is for,” Trump said.