Natasha Walter talks to Bebe Moore Campbell, whose new novel - dubbed the black Disclosure - takes on both racism and sexual harassment
Bebe Moore Campbell is reading from her new, bestselling novel, Brothers and Sisters, to an audience of about 300 people in Brixton. The scene she is reading portrays a middle-class black woman, Esther, advising a young girl on how to get a job: "And get rid of the braids!" Esther finishes. "When you're working for white folks you want to fit in, not stand out." Displeasure fizzes in the room. When questions begin, it's one of the first: "Do you really think she should cut off those braids?" Bebe Moore Campbell laughs. "No," she says. "I don't."

All the thorniest questions of racial identity are given a fresh airing in Brothers and Sisters (Heinemann). The bare bones of the plot are that the driven, antsy Esther, a fully paid-up member of LA's black middle class, is trying to get ahead in her banking job in the aftermath of the LA riots. She keeps trying to bounce through the glass ceiling, and keeps failing. She keeps trying to find her black Mr Right, and keeps failing.

In all her troubles, she begins to draw close to a young white woman at the bank, Mallory. And then, for the first time, a black man, Humphrey Boone, is taken on in a senior position in the bank. Esther is thrilled. Could this be her route through the glass ceiling, and even her Mr Right? Then Humphrey begins to come on to Mallory, and Mallory asks Esther to support her as a witness in a sexual harassment accusation. Who should Esther support, her white sister or her black brother? Why should she have to make such decisions?

Over coffee in a Mayfair hotel, Ms Campbell tells me that publishers were keen when she first mooted the idea of the novel: "Luckily, I put forward the proposal at a time when publishers had begun to confront the myths they had put about. Myth one: black people don't read. Myth two: black people don't buy books. Myth three: white people don't buy books by black people. The time I started on this novel, you had Toni Morrison, Alice Walker and Terry Macmillan all in the bestseller lists at the same time. And the publishers had to say, `Gee! Who's buying them? Who's reading them?' and regroup."

Indeed, the book has performed outstandingly in the United States: the hardback edition made the New York Times bestseller list; the paperback rights were sold for around $1m (£650,000), and the film rights went to one of the major studios.

Originally from Philadelphia, Ms Campbell first went into teaching, and spent many years trying to find her voice as a writer. Her first novel was never published, and she focused on journalism while she honed her style. But now, at 46, she is well known in the United States; for her first book of non-fiction, Successful Women, Angry Men: Backlash in the Two-Career Marriage; her memoir, Sweet Summer, and her first novel, Your Blues Aint Like Mine. But it's with Brothers and Sisters that she will break through to a British audience. Although the novel is steeped in the culture of LA, the issues it deals with punch right into our society.

Ms Campbell deals with the problem of affirmative action in a particularly direct way, showing both how essential it is for the black aspirers, and how dangerous it can be for inter-racial politics. One of her most unforgettable characters in this book is the white middle manager, Kirk, who is forced aside to make room for Humphrey Boone. Kirk falls into alcoholism and madness as he sees himself disenfranchised from his own society.

"I can see Kirk's point of view," Ms Campbell insists. "He thinks, why should I pay for what my ancestors did? I can understand that. But it's not what's most important. There is no question that affirmative action has been helpful in moving minority people into middle-class America. It won't solve all the problems, and it shouldn't be permanent. But I'm not yet prepared to trust to the fair-mindedness of employers in America, and lift the legal structures that bind them to employing people from minorities. After all, your natural inclination is to hire people you're comfortable with - most people are most comfortable with people who look like them."

Another problem that Ms Campbell tackles head on is one which she sees affecting all too many middle-class black women - where are their ideal partners? Her own first marriage broke down - in part, she believes, because her husband resented her growing success. And even though she is now happy with her second husband, a banker - who supplied much of the background for Brothers and Sisters - she can see that a lot of her friends are still dissatisfied.

"I see them making compromises that they didn't think they'd have to make. All of us grew up thinking there was a black prince for us somewhere. With a lot of professional black women, the princes are harder to find. Black males are not in higher education in numbers equal to black women. Black men are more likely to be victims of violence than any other group. Black women inherit those statistics in terms of a lack of marriageable men."

In the end, Mr Campbell's heroine does have to make a compromise, not of love but of status. She falls for a man who is kind, intelligent, funny and loving - and a blue-collar worker. But when Ms Campbell quotes Esther's original motto, "No romance without finance", during her reading, a storm of laughter and clapping greets her. Clearly, the women of Brixton recognise the problem.

Ms Campbell shows how even her most middle-class black characters are haunted by the Los Angeles riots. "There is never an excuse for rioting. But I can see the reasons for it. We don't own the shops and buildings around us. We don't have enough of a stake in our communities."

Seeing the potential success of Bebe Moore Campbell in Britain, her editor at Heinemann UK says hungrily: "Where is the British Bebe?" as though Britain isn't producing such writers. But Tony Fairweather of the PR company The Write Thing - who orchestrated a marketing campaign for Ms Campbell that brought 300 people to this venue even before publication, by leafleting everywhere from clubs to dentist surgeries - disagrees. "We have British Bebes already. We have Joan Riley and Merle Collins and so on. But some people always want to look across the Atlantic. British publishers are still stuck in the 19th century, they can't see how to nurture fresh talent, or market it."

It would be dismissive and patronising to see Brothers and Sisters as just a "black book". Told from the point of view of whites, Hispanics and Asians as well as black people, the story crosses racial boundaries, like all the good stories in the world. Still, Ms Campbell is keen to give back to her own community through her writing.

"I want my books to teach. And I am a kind of role model. I'm an example of hard work paying off. I went through five years of rejections before I first got a story published.

"Other black writers were an inspiration to me. When I was a child I never thought a black woman could earn a living through anything except teaching or nursing or cleaning. Toni Morrison gave me permission to be."

Although Brothers and Sisters has been compared to Disclosure, Michael Crichton's vivid, vicious fable about sexual harassment, Ms Campbell's book is a breezy, feel-good read in comparison. And despite everything, she can say optimistically: "I believe in the American dream! There are often stumbling blocks put in the path of minority groups, but I still believe in it."