No coy 'lit' openings for JM Coetzee. John Grisham couldn't have done it better."The blow catches him from the right, sharp and surprising and painful, like a bolt of electricity, lifting him up off the bicycle. Relax! he tells himself as he flies through the air …" It's the balance of the sentence, the delicate tip-toeing over the stepping stone 'ands', that alerts us to the fact we're in the hands of a Nobel laureate rather than a thriller writer, but, whatever the genre, it's the novelist's duty to snare the reader from the beginning and Coetzee has always been a master of that.

Having been thrown from his bicycle the Slow Man has come to a halt. Worse is to follow. The doctors try to save Paul Rayment's mangled leg but can't. It is amputated just above the knee. Papers are delivered to his hospital bed requiring his signature. "First the violation, then consent to the violation." Some of the questions prove surprisingly difficult. Is he insured? To the hilt. Old Rayment is nothing if not prudent. Does he have family? Of course he does. He has a sister, but she passed on 12 years ago. He has a mother too, and of course a father (but they both await the angels' clarion in their cemetery plots). Dead then, but as the Slow Man well knows, "those into whose lives you are born do not pass away". He would have liked to inform the authorities of this but there is no space on the form for extended answers. "Family: NONE," he writes. No children and no wife. There was one once but "she escaped".

Recovery is slow. His absent leg itches. "His cells are going out like lights." The nurses are kind and cheery but they exhibit an indifference to his fate. He and his ward-fellow "have nothing left to give to the tribe and therefore do not count." As Rayment's stay in the 'land of whiteness' comes to an end the theme of the book reveals itself. What if he had died in the accident on Magill Road? Would his death have made a difference to anybody - even to himself? Lying in his hospital bed he declares that The Great Judge of All will consider his life a wasted opportunity.

Back at home, under the care of a succession of nurses, his regrets come back nightly "like roosting birds". Chief among them is that he did not have a son. Why? Coetzee unpicks this one carefully. Rayment envisages himself and a 30–year old son out on a stroll, chatting. The Slow Man lets slip an oblique remark, something along the lines of it being "time to pass on". His son picks up the meaning at once. His father is ready to hand on the succession; call it a day. Paul Rayment has done his duty, now it is the son's turn to return the favour.

Perhaps, he considers, he still has it in himself to father a son. But since the accident he is unsure he has the seed and sufficient passion to drive it home. He is attracted by his Croatian nurse, Marijana. She is sensitive to his attempts to preserve his modesty, but, "when nakedness cannot be helped he averts his eyes so that she will see he does not see her seeing him."

So far so good. Seventy pages in we're sufficiently interested in Rayment and Marijana to have an investment in the development of their relationship. Marijana has a son, daughters and a husband. The reader settles lower on the sun bed, cool drink chilling the palm, content that there will be ample opportunities for a novelist of Coetzee's abilities to turn up the emotional heat over the next 160 pages and bring the narrative home to a satisfying conclusion.

But then a woman called Elizabeth Costello comes knocking at Rayment's door. She is in her late 60s and wears a floral dress cut low on her shoulders. He invites her in. She accepts a glass of water, settles on the sofa and recites to him: "The blow catches him from the right, sharp and surprising and painful, like a bolt of electricity …"

Rayment dredges his memory. Elizabeth Costello? It comes back to him. An Australian novelist (Slow Man is set in Adelaide). Once he had tried to read one of her books but it didn't hold his attention. He has since come across articles by her on ecology or animal rights. Once she was notorious for something but he can't remember what.

And soon she is demanding that he defend his amorous inclinations towards Marijana. Rayment is understandably annoyed. What right does she have? Why did she come to him? She replies that she didn't come to him, he came to her. "You occurred to me - a man with a bad leg and no future and an unsuitable passion …" And there's more. She explains that she has built her life by following her intuitions, "including those I cannot at first make sense of. Above all those I cannot make sense of …". So, Mr Coetzee, we meet at last.

Writers too often operate in their comfort zone. Not Coetzee. He is out on a very long limb here. Longer perhaps than the one he went out on for his previous novel (sorry JM, not a very elegant way of putting it but you get the drift) - the quasi-philosophical work of non-fiction masquerading as a novel.

Remember it? It was called Elizabeth Costello and it was about a 60–odd-year old Australian novelist. Probe further into his past and you discover that Costello first appeared when Coetzee was invited to deliver the 1997– Tanner lectures at Princeton University where he apparently ruffled a few feathers by using the fictional Costello as a device to deliver an impassioned lecture on animal rights. So has the seemingly innocuous tale of the Slow Man morphed into an exposition on creativity? And if it has, can he sustain it for a further 160 pages?

Rayment is next visited by a disfigured blind woman who has been delivered to his flat by Costello who has now taken up residence there. She is there to slake her own lust and to test his. The Slow Man's life is suddenly opened to new possibilities. "There is no need," he suggests to the nervous woman, "for us to adhere to any script. No need to do anything we do not wish. We are free agents."

Are we? Of course not. But in this profound, frustrating, remarkable novel Coetzee makes a good argument for the human capacity to find freedom within the constraints that box us all in; for the need to follow our intuitions. We are each of us the author and subject of our life narratives. But to live actively demands engagement with other members of the tribe, as the Slow Man finally comes to understand.