Serene, regal and comfortably afloat on a steady stream of achievement, Toni Morrison is unmistakable as she wanders through the leafy enclosures of Princeton University. She moves slowly, as though short of breath, and her silvery braids have the pallor and intricacy of a wasp’s nest. Students point at her, whispering as she passes. It is not just her blackness in this citadel of white privilege that is so striking; it is more that this granddaughter of an Alabama slave radiates an essential vitality, a difference.

There is no one quite like her in the US, no one rivalling her status as, to echo The New York Times , the “nearest thing America has to a national novelist”, no one who has done more to destabilise the literary hierarchies, while giving voice to the historically dispossessed. She is, in every sense, the new empress of the blues.

Today Morrison is accompanying Seamus Heaney, a fellow Nobel laureate, to a poetry reading; tomorrow Gabriel Garcia Marquez - invited by Morrison in her role as a teacher at Princeton - arrives on the campus for a week of seminars.

At times, Princeton seems like a club for famous writers - the Japanese novelist Kenzaburo Oe, a fourth laureate, is also on campus. But none is as famous as Morrison. Since the publication, in 1970, of The Bluest Eye , her fine first novel, she has, again and again, compelled Americans to confront that part of their history they would rather forget: slavery. In doing so, she invented her own idiom, found a new way of writing about her own culture in a style she proudly calls “indisputably black”.

Her prose is loose, colloquial, a lexical fusion of standard English and the vernacular, of lyric and street language, of the formal and folkloric. Critics speak of her singing voice, of the music of her dialogue.

Paradise (Chatto & Windus, £15.99), her seventh and most recent novel, is a study of a small all-black township, Ruby, founded by former slaves. It roams restlessly across the decades and its central event concerns the massacre of a group of women at a former convent on the fringes of the town.

American booksellers have ordered more than one million copies. This is an astounding figure, the result partly of Morrison’s iconic status and partly of an enthusiastic recommendation from Oprah Winfrey. When I met Morrison at her New York apartment, she spoke animatedly of her hour-long appearance on Oprah . “Oprah uses her show to promote books to the kind of people who might be intimidated by bookshops, the people I want to reach and am keen to address.”

Morrison’s large, open-plan apartment is on the top floor of a converted police station, a landmark turn-of-the-century building in downtown Manhattan. It is simply furnished: just a couple of bookshelves, a television, sofa and chairs. She has another house across town on the Hudson River and an apartment in Princeton.

In conversation, she is engaging and attentive, laughing often. She is open about most things apart from what she refers to, curiously, as her companion life. “You can’t be serious asking me that,” she says, responding to a question about whether she has a partner. “It’s none of your business. My sexual, my companion life, whether I walk around barefoot in my house - that’s mine, all mine. I fight tooth and nail to protect that.” She seems to relax only once the tape recorder is turned off, after which we talk for hours.

She began writing in the mid-1960s to “forestall melancholy” after the disintegration of her marriage to Harold Morrison, a Jamaican architect with whom she had two sons. At first, she wrote tentatively, in stolen moments. “I was very startled by this compulsion to write. I didn’t know where it came from. My life in publishing (she was an editor at Random House) was very fulfilling. I didn’t need to add anything to it. Only when I completed The Bluest Eye did I realise that I needed to have this thing going. But I still didn’t think it would have a central role in my life, because I was completely focused on my children and job.”

She pauses, then offers this thought. “Can you name a great woman writer who was a mother?” We begin batting names back and forth across an invisible net. Virginia Woolf, the Brontes, Emily Dickinson, Edith Wharton, George Eliot, Austen: all childless. She has a point. “But you see, I had children and a job. It was difficult. It’s always been different for men: they might have wives and families but they’ve been able to focus the central part of their lives on their work. Until recently, women couldn’t do that.”

The Bluest Eye was published into a vacuum; there was very little, if anything, to compare with it in contemporary fiction. If Morrison had a literary precursor, critics couldn’t name her. “My book appeared out of nowhere and went nowhere,” she says. Yet this account of the struggles of a young black girl who is abused by her father and who longs to have blue eyes has a fierce originality. It prefigures many of the concerns of her entire oeuvre: the burden of guilty memory, the corruption of American innocence, fractured identity (her characters fight to discover the truth of their African heritage), the unreliability of historical narrative.

Talking to Morrison, you realise how much she was hurt by the response to her first book. “What was so frustrating was that it was embraced as being representative of African-American life. No one reads Lolita as if it were typical of white girls. My book was about incest; it wasn’t a children’s book. Yet it was taught to children as offering a good look into the black family. I was horrified.

“The criteria for black writers were so different. We were seen as exotic or as revealing fundamental sociological truths about our community. But I wanted to write about race without being told that I was producing case studies. That took away the whole world for me.”

Toni Morrison (her real name is Chloe Wofford) was born in 1931 in Lorain, Ohio, a gritty steel-mill town. Her father, a poor but determined welder, was deeply pessimistic about race relations. “He disliked most whites,” she says. “He thought they were genetically corrupt. But my mother was more hopeful. She believed in education and the potential of America.”

At 17, Morrison moved to Washington DC, where she attended Howard University, the distinguished black college. “I was eager to go,” she says. “I was successful at high school and wanted to be surrounded by people who knew where I was coming from. Or maybe I just wanted to be around young black men.” She is becoming dreamy, her voice soft and coy. “Hey, that side of things was fun, too, now I think about it. How quickly you forget those pleasures.”

After graduate work at Cornell, she returned to Howard as a teacher, moving into publishing in the 1960s. As she approaches 70, Toni Morrison is enjoying every moment of her celebrity. At her New York launch party, she sat alone at a table receiving a long line of admirers. “Is she still sitting on her throne?” joked David Dinkins, the former Mayor of New York, as he stooped to kiss her hand.

She hangs out at parties with Tom Cruise, and talks about her work with Marlon Brando on the phone. Hollywood producers bid, in expensive auctions, to buy the rights for her books. All this and the Nobel Prize, too. Surely it’s time to give up the day job?

“I’m a child of the Depression. I’m scared of doing nothing,” Morrison says. “My father taught me that unemployment was a bad thing. Give me a stipend, a little office and a little bit of health insurance - I’ll be fine. Writing is my work but not my job.”