THERE is something that runs through Stevenson's characters," says Ben Okri. "There's a tone of voice, certain words. Words like this: I was angry. I was a little envious of'. It's there in the narrator of Treasure Island, Jim Hawkins. It's ever there in Dr Jekyll."

Okri, his voice treacly and reassuring, like that of a lawyer revealing the contents of a will to a soon-to-be-disappointed family, is explaining how some writers have the ability to create worlds while others must make do with describing them.

"Stevenson," he continues, since he has been re-reading his revered RLS, "can do it just by the tone of his voice. Some people can do it in a sentence. If there's one thing I've always liked about what we do as writers it is the creation of worlds. Some people prefer the pyrotechnics of language. And I love good language, truthful language. But the most important thing for me is the creation of a world."

It is late on a summer's afternoon in central London. Okri, whom I have known for more than 20 years, since he was a struggling young writer with a gargantuan appetite for pizza, had suggested we meet in the opulent bar of the Langham Hotel, a watering-hole for the more well-heeled employees of the nearby BBC.

"You think I am not stylish?" he teases. Okri, even when impoverished, always had an innate sense of style, like Nelson Mandela. Today, aged 48, he is garbed in the spectrum of grey and his beard is meticulouslytonsured.Heglidesratherthan moves, weaving waiter-like across the room. Were he taller, he could grace a catwalk. As it is he is built like a welterweight. I doubt though whether he would sanction that analogy. "If I were a boxer," he once said, "I would be Rocky Marciano not Sugar Ray Leonard." He is not, he insists, magical or dreamy, labels often attached to his work. He prefers to think of himself as hard-edged.

As I do. Okri is best known for The Famished Road, his fifth book, which won him the Booker Prize in 1991. Epic in scale, its main protagonist is a spirit child called Azaro who crosses with ease the invisible boundary between the living and the dead, as Okri does between the "civilised" west and Africa. Born in Nigeria, he was brought up initially in Britain. When he was seven, however, he returned to Africa.

His father, who died in 1998, was a minister in his youth. "He was a very, very powerful preacher." Then he became a lawyer. Then he decided to return to Africa. "Then he became an Africanist. He went back to the gods. He became your quintessential African. He just went back and embraced the land, the gods, his ancestors, and that was quite astonishing for me because it was a complete re-immersion."

Okri's early life was thus one in which he moved between two seemingly incompatible worlds with competing values, polar cultures and different ways of seeing. His father, he says, bestrode both.

"He was a latinist. This man was a classicist for goodness sake. He spoke Latin perfectly. Everything he taught me, there were two pillars: the classical tradition and the African tradition. And these were the two pillars on which my education was founded."

It is from this perspective that Okri's latest novel, Starbook, sprang. "This is a story my mother began to tell me when I was a child," it begins. "The rest I gleaned from the book of life among the stars, in which all things are known."

What exactly his mother, who died some 12 years ago, told him is unclear. At most, it seems, it was the stripped bones of a story. "Ben, did I ever tell you that ..." , she'd start, and then get distracted. Nevertheless, he says, he's been carrying it around for years, without having the "nerve" to write it.

"I kept meaning to ask her to finish the whole thing but one thing or another happened. There's that. An unfinished story is the genesis of the book really. But then another unfinished story was when mum went. And you know how it is when mothers die, they take away all your history, don't they? So much about you that you need to know and haven't asked. And nobody else knows it; they take it with them. That was the second impulse. So really it's an exile myth. It's trying to recreate what was lost. That's the real impulse behind it."

Starbook is set in an unnamed place and peopled with unnamed characters. There is a prince and a maiden who fall in love. The language of the story is simple, courtly, timeless, childlike, beautiful. One thinks of fairytales, legends, myths. Readers must imagine what this world is like for themselves because Okri gives few clues. Is it Africa? More likely than not. There are alligators and exotic birds, soothsayers and sages, anchorites and hermits, deep forests and ageless villages.

It seems idyllic but it is not. It is a world in which love leads to death and violence. It reads, too, like an allegory for our times in which one group of people feels free to seek dominion over another. But it is also evocative of the slave trade when people were wrenched from their homeland and transported thousands of miles away.

The story of the slavery, says Okri, is usually concerned with what has been taken away from a place, and not with what was lost from it. "Just the sheer quantity of talent, souls, energy, different world views, just lost to that land. So in a sense it was the earliest kind of spiritual drain of the land. There are two sides to it. And one only gets the outside story - the suffering of the slaves. But not what they were. Not their humanity. Not their groundedness in the place. Not the civilisation which they came from."

Added to which, he says, there is "the story of our times", which he articulates as "the murder of god. How we killed god. It's not the death of; it's the murder of. It's there. It runs through this book. It's a benign presence. In a way you have the creation legend, then you have the opposite of that - the destruction of the creation legend, which is what we're living through."

Little wonder, therefore, that Okri - who might have followed in his father's footsteps and become a preacher - took his time before tackling such huge themes. Now I see where he is coming from: the Greek philosophers, the oral tradition of Africa, the tribal elders with their "Buddha-like tranquillity", the Bible, the plays of Shakespeare, the poetry of Milton and Eliot, the novels of Dickens, Stevenson, Achebe and goodness knows who else.

What he has created, however, is a unique and beguiling world of his own imagining, which some readers may find hard to see themselves living in. How receptive does he think contemporary readers are to such stories? Ben Okri answers as he often doeswithanotherquestion."Doesonereally concern oneself about that?"

Starbook is published by Rider, £12.99. Ben Okri is appearing at the Edinburgh International Book Festival on August 24, 2007 at 1.30pm