'History is replete with monstrosities that shouldn't have happened. But they did. And we are what we are because they did,' writes Ben Okri in the opening pages of his ninth novel, a dreamlike narrative built around the ravages wrought by slavery on Africa. 'In the presence of great things glimpsed in the book of life one can only be silent and humble. The ultimate meaning of history is beyond the mortal mind. All one can say is that this happened. Make of it what you will.'

Okri, 48, continues his fascination with African legend, most effectively harnessed in his 1991 Booker Prize-winning The Famished Road, with Starbook - A Magical Tale of Love and Regeneration, purportedly a story told to him by his reluctant mother about 'a girl by the river in Africa' and her encounter with a prince 'who went searching for God'.

As the title suggests, this is a love story, but it's also about the origins of inspiration, the portentous power of dreams and the cost of memory, and about slavery that robbed Africa of generations of young men and women and irrevocably changed its future. 'To remember,' the reader is told, 'is the worst form of suffering.'

Okri's magic is that Starbook, his first novel in five years, operates on a number of levels, transgressing time and place, imagination and reality, as he weaves his compelling, insightful and deeply disturbing story about the nature of humanity.

At one point he asks: 'When people sense their own extinction, what do they do?'

Some could see in their dreams the white spirits and what they were doing and 'spoke of chains of iron; they spoke of instruments that spat out fire and death; they spoke of long lines of young men and women of the land being flogged and gagged; ... they spoke of trails of blood that ended at the sea.'

Okri introduces early 'a great wooden sculpture of three men and a woman bound together by chains at the ankles, in positions of intolerable lamentation and humiliation, and yet rendered with stoic dignity, as if gods had been made the slaves of fools'.

'The sculpture seemed to speak of a great world calamity, a tragedy of vast proportions, so vast, in fact, that it threatened the world. It seemed the world would never be the same again because of the tragedy and intolerable sorrow and noble suffering that the work breathed out in its broken proportions and the agonised shapes that broke the heart and yet still spoke of divine revolution beyond human understanding.'

Starbook isn't an easy read, at least initially, requiring some adjustment to Okri's poetic prose, which when given full rein emerges as word-perfect sentences of a hundred words and more. This isn't a book for those with short attention spans. Nor is it one for the weak-hearted.

Okri recounts the maiden's dream of being in a ship 'in its bowels, in chains, lying upside-down, or sideways, facing the feet of another, who was also chained. Blood on the chains was like rust ... Wailing sounded everywhere in the crushed space, and women were dying, calling out the obscure

names of their ancestors in languages no one understands. And death and doom was thick in the dream as she floated and saw hundreds of bodies like writhing ebony sculptures bleeding and drowning in the white waves.'

And the prince knows from his dreams: 'He had survived the monstrous crossing of the sea of evil, where slaves lay chained ankle to ankle, wrist to wrist, in the coffin of the hold, in the ship, on waves of an empire's dream of power. He had arrived in a new land that was rich with blood and guilt and hope. He had survived the lash. He had survived the degradation. He had survived being less than a man, or a dog, or an insect, or a beast. He had survived the loss of his love, his kingdom, his home, his earth.'

Yet Okri isn't without humour. 'Children do not always live up to the possibilities we see in them,' the maiden's mother explains to her daughter. 'Often they let their parents down and grow up to become quite ordinary, quite like the others.'

And throughout are his observational gems about humanity. 'We never change. From youth to adulthood, from frivolity to seriousness, under the impact of significant experiences we only become what we really are, for good or ill. That is why when people say they have changed it does not, as they think, mean that they have necessarily changed for the better.'

Okri has made use of Starbook to explore some big ideas, such as when the Prince realises happiness and joy are the result of past and future suffering, 'a sublime compensation for enduring the unendurable'.

He further writes: 'Man enchained and gagged with metal and enslaved ought to be the symbol and icon of a new religion: one that reveals how man's life was sacrificed for the wealth of others. And the building of civilisations.'