We all love a juicy literary scandal, and there have been plenty of them recently involving memoirs. But the latest concerns a famous novelist and an even more famous movie star.

Rachel Cusk’s new novel, M, is about an actress whose beautiful face is everywhere. She is observed by an author, something of a friend, who has her permission to write about her. What emerges is a portrait of a woman who lives a luxurious yet unreal life, seems unreal to herself, and tries to make connections that might enable her to become a human being.

Even before the book’s release (September 1, in Australia), rumours were flying around Hollywood that the mysterious M was none other than Natalie Portman, reportedly a friend of Cusk’s and a fan of her writing: she promoted Cusk’s novel Parade on her Instagram book club and talked to her online about her novel Second Place. They both live in Paris.

Many pointers lead to Portman. One is that the actress M began her career as a child and some explicit sexual scenes in her first film were cut at her mother’s request. Portman first acted in Luc Besson’s 1994 Leon: The Professional when she was 11 and 12. Her mother demanded cuts in the script. Another is M’s starring role as a “vulnerable and self-torturing ballerina” in a film that “brought her a new kind of glory” – much like Natalie Portman’s role in Darren Aronofsky’s 2010 Black Swan, for which she won the best actress Oscar. Plus, there are the luxury campaigns M features in “wreathed in the pink flowers of spring” which are like those of Portman’s Chanel ads.

Life of M opens with the unnamed narrator recounting how she told M she wanted to write her biography. “’She liked the idea. She’s a good sport. Would you just make it up? she said,” the narrator reports. But the goodwill fades as the project continues; in Cusk’s novel, the actress grows angry and betrayed – “She didn’t seem to like it all that much”.

Rumour suggests that might also be the outcome in life, though so far, neither Cusk nor Portman has made any comment.

What does this episode say about an author’s right to mine another person’s life for their fiction, even with that person’s permission? We hear a lot these days about autofiction, a kind of creative writing close to reality: perhaps only the names are changed. But writers have been doing this for a very long time.

Sometimes they have petty revenge in mind, scores to settle, an urge to tell their own side of a story. Other times they are fascinated and inspired and want to explore people they know in more depth on the page. Or they want to confess their own failings. All these motives can exist together.

Her writing is acclaimed because of its relentless drilling down below the surfaces of personality and character.

Ernest Hemingway’s first novel, The Sun Also Rises, was unashamedly about himself and a group of friends in Spain in the 1920s. The friends were horrified when he revealed that two of them were having an affair.

Truman Capote came undone when he exposed secrets about his lady friends in high society in a novel he never finished. When an excerpt was published in Esquire, he was banished from their magic circle.

More recently, Philip Roth and Karl Ove Knausgaard, in their very different ways, made brilliant careers out of writing tell-all fiction about themselves, their wives, their families and friends, and had to weather the consequences, including threats of legal action. Roth made a few threats himself.

Indeed, Cusk has already faced challenges from people who felt exposed by her writing. The first run of her 2009 novel The Last Supper: A Summer in Italy was pulped because she was threatened with a lawsuit for breach of privacy. And author Damian Barr complained he was the character Julian in her 2017 novel Transit.

I feel for these people, but ultimately, anyone who knows anything about Cusk’s work can’t expect to get an easy ride. Her writing is acclaimed because of its relentless drilling down below the surfaces of personality and character, exposing people’s buried desires and sometimes a longing, as in M’s case, to discover who they really are – or even if they exist at all. Friends of Cusk: you have been warned.

What else is happening in the book world?

• This is the email many authors dream of getting – but beware, it could be a trap
• Artist Tom Carment reflects on five decades of friendship with the late Robert Gray
• Novelist Richard Flanagan opens up about his early-onset dementia misdiagnosis
• A 3000-year-old poem is suddenly back on the bestseller list. Here’s why