'I don't think I've exorcised the Shaking Woman. This is an aspect of my neurology and I can't expect it to go away. She's me'

In the summer of 1982, Siri Hustvedt and her husband, the novelist Paul Auster, were on their honeymoon. The pair were walking around a gallery in Paris when Hustvedt felt her arm suddenly jerking up and back, slamming her into a wall. She experienced, briefly, a feeling of absolute euphoria, then a "horrifying" migraine that lasted for a grim year in which she was closeted with a series of doctors, and even briefly hospitalised.

In her new book, The Shaking Woman, part-memoir, part-scientific investigation, Hustvedt addresses a personal history that has been marked by both extensive literary output (four novels, two collections of critical essays, poetry) and acute neurological upheaval. Subtitled "A History of My Nerves" (a delicate, fretful word, redolent of smelling salts, which sits well with her pale, attenuated beauty), it opens with Hustvedt giving a memorial address for her father, two and a half years after his death. A seasoned public speaker, "confident, and armed with index cards", she nevertheless found herself "shuddering violently from the neck down . . . as if I were having a seizure". Shocked, she struggled to the end of the speech – at which point the shaking subsided. The incident jolted her so deeply that it led her to reassess a lifetime of tremors and pains. The Shaking Woman is her attempt to make sense of her past, and by doing so to discover who this "shaking woman" is, and why she chose to appear then.

Along the way, it also becomes the working-out of a duality. Hustvedt is both the shaking woman of the title, and the thinking woman, the "I" of the book, who attempts to comprehend her. Fortunately, duality is safe territory for her. The daughter of a Norwegian mother and Norwegian-American father, she spent her childhood tugged between two languages: when the family were in the US, her Norwegian vanished; during stints in Norway it bubbled up again, flooding her English out. In 1972 she moved to Norway for a year, staying with an aunt and uncle and studying in Bergen. "I'd been there just a couple of weeks; the Norwegian had come back. Then, this one night – I ­remember it clearly – I dreamt in Norwegian, but with English subtitles."

As a metaphor, it's almost embarrassingly neat. "Dreams," Hustvedt agrees, "can be incredibly efficient. This one encapsulated precisely what was going on in my life." But just as in the landscapes of her novels, in which objects and scenarios are striated with meaning, the neon-lit message – that Hustvedt saw herself suspended between two countries, and had to sublimate part of herself in order to shift from one to the other – is only part of the story.

On the one hand, the subtitles also suggest the urge to ransack a situation for meaning which led directly to The Shaking Woman. On the other, their presence functions as elegant shorthand for those divisions within the self which have informed her work and intellectual life for as long as she can remember. "People who grow up with two or more languages understand that each can express certain aspects of reality better than the other," she says. "You're forced from the off into a dual perspective; you're always shifting your point of view."

The directions her life has taken mean that Hustvedt is more practised than most at seeing herself as an ensemble cast. As well as her American and Norwegian selves, there's the Hust­vedt who's an author in her own right, and the Hustvedt who's married to Auster, for many years the better-known, more successful writer of the couple (there's also the Siri who appears in his novels, and the various permutations of herself who crop up in her own).

Furthermore, she has also had to contend with being both the Hustvedt who's pretty and the Hustvedt who's very smart. It's a balancing act which remains tricky for a woman to pull off, as she acknowledges through the ­character of Inga in her most recent novel, The Sorrows of an American. In one scene, Inga – beautiful, Scandinavian – remembers a point in her marriage to Max, an acclaimed novelist, when she was concerned about her own book being "attacked, or worse, ­ignored". "I was never taken as seriously as I wanted to be," Inga says. "I started wishing I were a man. I wished I were ugly."

The parallels between Inga's life and her creator's are unmissable, and, as an author, Hust­vedt happily acknowledges her role as the architect of endless alternative selves. "Novelists embody plural selves all the time," she says. "What are characters, after all, if not other selves?" It's an impulse which, she thinks, stems from the childhood drive to create; she sees something Peter Pan-ish in the disposition of the novelist that allows this playing to continue. "We're still making people up, acting out the mom, the dad, the baby. The malleability of self in play, the possibility of becoming another – that's the life of a novelist. In my case, there's always some connective tissue that brings me to a narrator, something I feel close to. But you can spend years living another sort of life."

In a sense, she's done that anyway. Hustvedt grew up in Northfield, Minnesota, a modest midwestern river-town whose motto is "Cows, Colleges and Contentment". The town, like many in Minnesota, has a strong Norwegian community; Hust­vedt's father, Lloyd, was professor of Norwegian studies at St Olaf College. "There was always Norway, always the other place." But throughout her early life, New York was there, too, as "an idea, a fantasy of urban existence". In 1978 she was awarded a fellowship at Columbia, and struck out east. On her arrival in the city, she says, "I didn't know a living soul. I had this tiny room right on the border of Harlem, and for the first three days, I stayed in and read Crime and Punishment, as if I had to shore myself up for this new experience. After that, I started exploring. I've been here over 30 years now."

Hustvedt and Auster met in New York in 1981, at a poetry reading. "A friend pointed him out, and said 'That's Paul Auster'," her voice drops, mock-solemn, "'the poet.' And I thought 'uh-uh'. The family joke is that it took me about 60 seconds to fall really hard, and it took him several hours. It was a really fast bit of business."

The year following their marriage was tough. "I felt a lot of guilt," Hust­vedt says. "I thought there must be unconscious motives – you know, you get married and suddenly you're sick for a year? It took me a long time to give up that idea of self-blame." But despite the difficult start, they forged a partnership that carries on to this day in the couple's bohemian-luxe Brooklyn brownstone. When they met, Auster was already working on his first prose work, The Invention of Solitude, and Hustvedt was writing poetry (she published a small collection, Reading to You, in 1983). But she was feeling the urge "to write something with an uncanny feeling, something unheimlich", which would become her first novel, The Blindfold. "We're each other's first editor," she says. "If something's not working, it's wonderful to have a reader you can trust to say 'actually, you've gone off the deep end here'. It's worked because we both believe in the other person's project: it's not like you're ripping away the underpinnings of the person's ego. Ours has been a good literary friendship."

Hustvedt began writing The Blindfold in 1986, a year before the birth of her daughter, Sophie; it finally came out in 1992. By this point, Auster had published more than half a dozen novels, including the New York trilogy, and was being touted as one of the city's hottest writers. While this caused problems for Hustvedt in the sense, as Inga puts it, of being "taken seriously" in her own right (it's still a rare review that doesn't mention her marriage), Auster's early success wasn't an issue between the two of them. "It's not as if I've been unlucky," she points out. "My books have been published and ­reviewed. I haven't lived through terrible literary suffering!"

Not that the ride was always smooth. While The Blindfold was well received – Don DeLillo praised it as "a work of dizzying intensity" – Hustvedt was deeply stung by one journalist's claim that Auster must have written it for her. She can laugh about it now ("It was tantamount to the psychosexual ­narcissistic rage thing!"), but it's no surprise, perhaps, that journalists don't come off too well in her work (the grotesque Linda Fehlburger, who sniffs around the pages of The Sorrows of an American, digging through garbage cans, "fishing out papers and letters", is a case in point). "I guess some of those characters are as close as I get to monsters," she nods. "Though the only monster I've ever really made is Teddy Giles. None of my journalists are as bad as that."

Giles appears in Hustvedt's third novel, What I Loved. If The Blindfold and its follow-up, The Enchantment of Lily Dahl, brought critical acclaim and moderate sales, it was What I Loved that catapulted Hustvedt centre-stage. "Like most writers, on one level I was just happy to think 'Good – they noticed me! Yay!'" she laughs. The labour that went into the book made its reception even more gratifying. "It took me six years to write. I redrafted it over and over," she remembers. "It just wasn't good enough; the tone wasn't right. Finally, in that last draft, I hit it." How did she know it had worked that time? "You feel it. It's a strange thing about writing fiction; there's a sense of rightness and wrongness. Then Paul read it, and he agreed, which was a relief." Despite the grind, however, at no point did she consider throwing the thing over. "It honestly never occurred to me. I'm kind of dogged. There's a stubbornness that helps you get through six years of trying to make it work."

That stubbornness must have come in handy after the book's publication. While the reviews were effusive (writing in the New York Times, Janet Burroway called it "a rare thing, a page-turner written at full intellectual stretch . . . large-minded and morally engaged"), much of the babble around its appearance focused not on the writing but on the writer, and the perceived correlations between her life and her characters'. The novel tells the story of Bill Wechsler and Violet Blom, a handsome, cultured New York couple – he an artist, whose odd, brilliant works lend colour and texture to Hustvedt's prose; she a researcher into modern manifestations of hysteria. Bill's son, Mark, by his first wife, the chilly Lucille, grows into a charming but morally slipshod adolescent, an easy liar, a petty thief. He falls under the sway of Teddy Giles, Iago of New York's art scene, and the two are caught up in the murder of young runaway Rafael Hernandez.

Taken point by point, as a now-­notorious piece by Joe Hagan in the New York Observer did, the parallels are evident. Before his marriage to Hustvedt, Auster married and had a son, Daniel, with the writer Lydia Davis. In 1998, Daniel was sentenced to five years' probation for stealing $3,000 from a deceased drug dealer, Angel Melendez. Melendez had been murdered and dismembered by a party promoter, Michael Alig; according to a report of his courtroom plea, Daniel admitted to having been in Alig's apartment at the time.

"One must fight the temptation to conclude that What I Loved is Ms Hustvedt's way of expressing her unvarnished feelings about Daniel Auster and his birth mother," Hagan concluded. As a piece of literary criticism, his verdict is startlingly uninflected; certainly, it gives no sense of the subtlety of a novel in which Bill and Violet's story is only one of several strands. "Most of this stuff is generated unconsciously," Hustvedt says now, of her subjects, "You're aware to some extent of what you're doing – you don't write blind – but there's something strangely ruthless about art. Unless you're actively censoring yourself, this very strong, emotional, dreamlike material emerges." On the specifics of What I Loved, she declines to be drawn. "I made a decision that I was never going to say a word about it, and that's what I've stuck to. As I said in The Sorrows of an American, there are always things that are hidden. Some things just aren't for public consumption."

Nevertheless, The Sorrows of an American saw her locate herself explicitly in that unstable hinterland between memoir and fiction. The novel, which is narrated by psychiatrist Erik Davidsen in the year following his ­father's death, was written as Hustvedt's own father was dying; in it, she draws directly from his life, incorporating his diaries into her text. It wasn't until after publication that she asked herself why she hadn't written a memoir. "Writing as myself," she says, "I'd have been in danger of slipping into my adoring seven-year-old self, gazing up at the great man. I needed to avoid that, to get a more complex portrait." Was his presence in the book an act of ventriloquism, or a way of carrying on a conversation? "I think the impulse – which I was only able to articulate fully later – was for resurrection. Having him there became part of grieving. At the same time, you finish the book, your father's still dead. It's not therapy in the sense of recovery."

The same is true of The Shaking Woman – in many ways a companion piece to The Sorrows of an American, in which the same questions are considered from a scientific rather than a literary point of view – and it's one of the things that makes it an interesting, even unsettling read. One comes to it expecting an answer, a resolution – and finds, not an answer, but acceptance. "There are pre-set cultural narratives about suffering and triumph: someone who's been beaten or is an addict triumphs over their adversities by the end of the book," Hustvedt says. "There's nothing inherently wrong with that, but the fact is, many people don't overcome their illnesses. I don't think I've exorcised the Shaking Woman. If there's any ­closure – and it's a word I detest – it's the recognition that this is an aspect of my neurology and I can't expect it to go away. She's me."