Mention his latest Booker Prize shortlisted book, On Chesil Beach, which tells the story of a sexually inexperienced English couple and their disastrous wedding night in the early 60s, and he instantly asks, 'Don't you think we rather exaggerate to ourselves the extent to which all that repression is behind us? We have a mass media that's presenting so constantly everybody having a wild and fulfilling time. Yet we know that there are these shivering individuals full of apprehension and their fears and self-doubt are not represented. People say, well, you couldn't write On Chesil Beach set in the present. I think you could.'

McEwan, appearing at a sold-out Hong Kong literary lunch on Tuesday, should know. He has had innumerable letters from people about the novel since its release. Many are from young people, others from people married in the 50s, he reports.

One letter that struck him in particular was about a couple whose wedding night was so disastrous, their ignorance so total, that when they returned from their honeymoon they went to see a doctor and asked him to tell them what to do. 'There's something rather touching about that,' says McEwan. 'It makes you think how did the species survive and how did we come this far.'

He adds, 'Living in very ethnically mixed, culturally mixed London, I could imagine that you could write a similar novel about a young Muslim couple who are suddenly left alone on their wedding night to sort it out for themselves. I could think of many other communities in which that might be the case. All the social and cultural expressions would be different but I think the underlying matter is universal: that we're not quite as bold and free as we make out.'

It is perhaps no surprise, given the extraordinary success of his 2001 novel Atonement, about lying, guilt, reparation and the nature of perception and writing, that he has already been approached by several filmmakers about filming On Chesil Beach. Not that Atonement is the first of his 11 novels to be filmed. But for McEwan, it trumps a list of adaptations of his novels that includes The Innocent, The Cement Garden and Enduring Love.

He took on the role of executive producer of Atonement so he could have some say in the process. 'I didn't want to do the screenplay, yet I couldn't quite walk away,' he says.

But despite the immense pleasure he takes in Atonement - which has been nominated for seven Oscars - he has reservations about adapting On Chesil Beach.

'My response is always if someone wants to, fine. But it is very hard in movies to represent that inside quality, the thoughts and the seeing self from the inside. The difficulty I think is to get right the swirl of feelings, the emotional truth of what each character is privately thinking set against what they are actually doing and saying out loud: the distance between what they want and what they appear to want. That's the thing, I guess, that only novels can really do.'

For a small 166-page novella, On Chesil Beach certainly packs a powerful emotional punch. Written in taut, mesmerising prose, it captures one night, an entire era and two lifetimes in a few scenes. Yet its hardback and paperback sales look set to eclipse those of Atonement, which is widely acclaimed as a contemporary masterpiece and, before the release of the film, sold more than a million copies.

The fifth of his novels to be shortlisted for the Booker Prize, including his Booker Prize-winning 1998 novel Amsterdam, On Chesil Beach confirms McEwan's abilities as that rare kind of novelist who can convey the complexities of a moment, a character, or an entire age with a few strokes of his pen. He is also the kind of writer who can find himself at the centre of controversy without even trying. He made international headlines when he recently discovered he had a brother and found himself at the centre of a short-lived global media blitz when he was erroneously accused of plagiarism in writing Atonement.

Along with the critical accolades and his ever-increasing popularity in Britain and in Europe has come endless speculation about his private life, the nature of his divorce and remarriage and what he describes as 'obligatory for anyone writing a review', a continual harping on about the dark themes of his earlier novels.

'I've learned to live with it but I find it tedious,' he says. 'It does seem to take up a lot of time and space.' His 2005 novel Saturday in particular was seen by some as an open invitation to speculate on his personal life, with some critics mistaking the views of his central character, Henry Perowne, for his own.

'It comes with the territory. No novelist is going to escape being pissed on every time he publishes a book. I mean, it's how it is. There's no way you can ever avoid it,' he says. 'And just as you shouldn't take that too seriously, nor should you take the praise too seriously either. It's better to be wary of both.'

There is no doubt his reputation as an outspoken atheist owes much to Saturday, in which he deliberately presents a kind of humane, atheistic view of the world. Then there are his many public utterances on the subject, including his essay in his friend Christopher Hitchens' latest book, The Portable Atheist.

'It's the term I'm going to have live with,' he concedes. 'I'd no more wish to be called an atheist than a southern American Baptist would want to be called an A-Darwinist, but I think its perfectly possible and clearly possible, self evidently so, to live a moral life without a god. And I think actually most Christians, most people with strongly held religious beliefs, actually operate on a moral system that is not selected from sacred texts but largely from a kind of moral sense that we have of the world, for which religion is just an expression.'

For a self-described rationalist acutely aware of his writing life, what is intriguing about McEwan is how readily he will confess to his superstition about first sentences. 'It is rather like building a wall and if you don't get the bottom courses correct it can fall over. And I have a near-suspicious sense that if you write the wrong paragraph you're going to screw up everything else.'

It is an anxiety about language that he attributes to his mother and one he first wrote about in his moving essay Mother Tongue. 'It's a troubling thought that a sentence is not doing what you think it is. It's so crucial, the first sentence, because you know you've invited someone to sit for eight, 10 or 15 hours with your imagination. So this is the door, the portico through which you must enter. I think a lot of my hesitation in writing has been about wanting to feel that I'm in complete control of the reader's response, and you know this is an impossibility. But I think I am driven by this wish still, to want to be as clear as possible.'

He is also frank about his personal journey from 'shiftless army brat' to the most celebrated novelist in Britain, but insists his 'is a well-trodden route'.

The son of a Scots army officer, he was the first in his family to go to university and before that grammar school thanks, he points out, to the welfare state.

'I felt to some degree that sense of alienation from your background that occurs when you're put through something and your terms of reference change and those of your family remain the same. It's not uncommon. And it's particularly acute when you're young. I'm amazed now when I look back at that young person who felt so strange and a little frustrated,' he chuckles. 'And I think, 'Oh you little prick, these people know as much as you do. They haven't read the books, but they've certainly been through the tragedies.''

Now 40 years into his writing life, he says, 'Writing has become such a habit with me that there's no getting out of it. Nor do I particularly want to get out of it: it seems like an extension just of being now. I sometimes wonder how it must be not to be a writer. I mean, to go through life and leave no trace of your consciousness seems rather odd.'

For McEwan, who attributes all forms of cruelty to 'a failure of the imagination', the writing of novels is a kind of moral act.

'Certainly at the level of drawing readers into the nature of character, into another mind. Knowing what it's like, feeling what it's like to be someone else is really a moral journey we make when we pick up a novel. But above all else, we should go to novels for pleasure.'

Writer's notes

Genre Literary fiction

Latest book On Chesil Beach

Next project another novel

Age 59

Born Aldershot, Hampshire, England

Family Married to Annalena McFee; two sons from a previous marriage

Lives London

Other works include Saturday (2005), Atonement (2001), Amsterdam (1998), Enduring Love (1997), The Daydreamer (1994), The Comfort of Strangers (1981), The Cement Garden (1978), First Love, Last Rites (1975), Or Shall We Die? (libretto for an oratorio by Michael Berkeley, 1983), Sour Sweet (film script based on the novel by Timothy Mo, 1988)

Other jobs a dustman (for several months while a student)

What the papers say

'McEwan's brilliance as a novelist lies in his ability to isolate discrete moments in a life and invest them with indelible significance.' - The Guardian (review of On Chesil Beach)

'Subtle as well as powerful, adeptly encompassing comedy as well as atrocity, Atonement is a richly intricate book.' - The Sunday Times

'Written with superb exactness, complex, suspenseful and humane, this novel reinforces his status as the supreme novelist of his generation.' - The Sunday Times (review of Saturday)

Author's bookshelf

Clarissa by Samuel Richardson

'Possibly the most detailed representation of human consciousness.'

Pride and Prejudice by Jane Austen

'Moral reasoning and aesthetic pleasure held in perfect balance.'

The Dead by James Joyce

'A beautiful meditation on mortality.'

Herzog by Saul Bellow

'Precise rendering of an extraordinary mind.'

The Rabbit Tetralogy by John Updike

'A whole society and half a century in four books of luminous prose.'