A searing novel and a sensational film has thrust Sapphire into the limelight

Shortly after the publication of her first novel, Push, which told the story of an obese, illiterate, black teenager abused by her mother and raped by her father, Sapphire was informed by a prominent African American magazine that it would not be featuring a review. Essence magazine's boycott was a defining moment for Sapphire. The story of Claireece Precious Jones, written phonetically in a vivid stream-of-conscious outpouring, remained below the radar for 13 years.

Then, in 2009, it hit the New York Times bestseller list after a film adaptation by Lee Daniels (entitled Precious) which stunned audiences at the Cannes, Sundance, and Toronto festivals, won two Oscars, and made an unlikely heroine out of Precious Jones. She finds freedom, of sorts, despite having two babies by her father and contracting HIV from his abuse.

Sapphire has a theory for why the book was disdained by Essence in 1996. "I think people thought maternal abuse made the black community look bad," she says. As one of the first books to lay open the character of the violent, sexually abusive mother-figure, it had perhaps too taboo a topic, although "I felt like saying 'I'm not trying to hurt you. Don't shoot the messenger'".

The then editor eventually wrote Sapphire a letter of apology. The magazine has, 15 years on, been among the first to review her second novel, The Kid (Hamish Hamilton, £12.99). An urban Bildungsroman featuring Precious's orphaned son, Abdul Jones, it is just as explicit, and damning, in its depiction of a forgotten underclass.

Push's story of illiteracy, undetected abuse and social deprivation was a deliberate reflection on the failures of the American welfare system. It is rare that these fringes of existence are ever exposed, co-existing next to extreme affluence, and there is always disbelief when they are, she suggests.

The same torchlight into the country's internal failures was shone during aftermath of Hurricane Katrina, which not only exposed the devastation caused by the disaster in New Orleans but also the poverty, helplessness and desperation endemic to the area long before the hurricane arrived. "It was a defining moment, when I saw the press standing in front of the cameras, asking 'is this our America?" comments Sapphire. "Push [the book] was saying 'yes, this is your America'."

While The Kid is a continuation of the family story, it does not extend Precious's narrative arc. Her story has already been told, says Sapphire. Just as there is, statistically, a far greater likelihood for poor black women to die of HIV-Aids in America than their white counterparts, claims Sapphire, so the opening of The Kid takes Precious's diagnosis to its final conclusion. We meet Abdul at the age of nine on the day of his mother's funeral.

The rest of the book sees him serially betrayed by the people and institutions paid to protect him, from foster parents to care homes to the welfare services to church figureheads. The "trap doors" are many, the ground forever moving beneath his feet, as he learns to rely on survival instinct over any sense of good or bad. Criminal acts are perpetrated by him, just as they were previously perpetrated on him.

Sapphire says this book "isn't the one that a lot of people wanted me to write" after Push. "There is a certain kind of expectation for women to write the romantic novel, and if there is a captivating character, there is the expectation that you are going to continue with it. I showed what I wanted to show with Precious, but people really wanted me to continue with her. African American people do not have the same access to anti-viral drugs. That's why she dies."

While the belated success of Push has been welcome, Sapphire felt deeply frustrated by those who confused Precious's life with her own. Born into a middle-class army home in California, Sapphire (who changed her name from Ramona Lofton) read avidly and held ambitions to write. Her mother though – "a woman of her time" – encouraged her to stop at reading: "She was of the view that if I loved to read and write, I could maybe one day become a librarian. I thought, 'Oh'. So the idea of being a creator wasn't there. I didn't have a clear concept of who the books that I read were written by. It was as an adult, in my twenties, that I started writing poetry."

It is often the case in black women's writing, she thinks, for critics to conflate the fiction with autobiography: "I'm not an animal howling out my pain. It is not my story." The Kid is no less emotionally charged than Push, but the central character's life simply cannot be compared to Sapphire's. We leave Abdul on the cusp of adulthood at 17, striving to become a professional dancer. He is intelligent, articulate, and determined, though his inner voice bubbles over with violent, sexually explicit fantasies. Yet the same misconception – incredibly – persists. "People tell me he sounds so authentic, like I am that little boy," she says.

She began conceiving Abdul's story shortly after finishing Push. The novel alludes to the rise of Aids and growth of the world's orphan population, as well as the bias and bigotry around adoption (there is a very low uptake of black orphans in America). These socio-political themes fuel the book, but do not overwhelm its raw emotional centre. Abdul is in some ways, "an African American Oliver Twist", navigating a route into adulthood and skidding between orphanages, care homes and the street. Dickens's many orphans (Oliver, David Copperfield, Pip from Great Expectations) influenced his creation, as did Dostoyevsky's Crime and Punishment, in its examination of morality and criminal guilt, and Richard Wright's Native Son.

Sapphire, who at 61 has the zeal and righteous anger of someone far younger, was a performance poet, teacher and activist long before becoming a novelist. There is a clear edge of social activism to her work still, though much more discernible in person than in her stories. She talks with a sociologist's insight about the legacy of slavery and disenfranchised communities. Unlike those writers who speak of the primacy of the imagination, she has referred to the intersection between literature, activism and therapy – how lives can be changed by what one reads, in its consciousness-raising and therapeutic properties.

Initial inspiration for Precious and The Kid came from the disadvantaged boys and girls that she taught at a literacy centre in Harlem in the 1980s. Precious was partly formed from a montage of the girls she met there, as were aspects of Abdul. One of the most pleasurable aspects of writing The Kid lay in the creation of dialogue, a melange of colourful street slang and hybrid patois. Abdul's interior language encompasses the stunning lyricism for which Sapphire is known ("The night sounds are like zeros that add up to nothing. Silence").

The vocabulary was gathered from the voices in Brooklyn's Sunset Park, where she lived until recently, which has a large multicultural population. "In New York, if I'm on the tube system, I'm constantly listening to conversations. I'm watching people go to work, watching them fall asleep coming home. "I think it's my job. I can't imagine being a writer and not being a listener. A lot of writers think it's a job to describe a scene but the advent of Google means the scene is there for anyone to see. The picture I'm giving you is what's inside a person's soul."

Another exhilarating aspect of the writing lies in Abdul's dance classes. He comes across an African dance class and joins an avant-garde troupe. Just as poetry provided psychic liberation for his mother, so dance has the same redemptive power for him. Abdul's entry into the avant-garde dance scene is not easy. The others in his troupe, far more privileged, are suspicious of his uncertain identity, his homelessness, his poverty, and perhaps envious of his talent. Sapphire sees his precarious position as typical. It is a world in which the black artist is still a token member.

That is not to say that things have not improved for black America, she adds quickly. A sea-change came with Barack Obama. To change the man at the top "is a big thing in democracy. We will see that in Egypt and Libya now. [Obama's election] was, to me, one of the most important events in American history. I grew up with the idea that that just could not happen."

Although this second novel has been 15 years in the making (she published two poetry collections before Push), Sapphire hopes to finish a third - possibly one that continues Abdul's story - in less time. It took so long because she was earning a living while writing it, and also because of the demands it made of her, and those she made of herself. As a result, it is nearly three times longer than Push. "I'm not one of those writers who is on a schedule with a book every two years. I want to let events come in. [For example] I was writing The Kid during 11 September and it's not there in the book, yet it is there - it eases itself in. It's good to digest ideas, and not just vomit them out."

Yet the passing of the years, though they may not show on her face or energetic demeanour, have left her with a growing urgency: "I am more driven to produce, to get it out. It's because I'm feeling a sense of my mortality."