In the middle of Sebastian Faulks's new novel, A Possible Life, at a clinic in Athens in the middle of the 21st century, two Italian brain scientists solve the mystery of human consciousness: "The thing that had given the world Leonardo, Mozart, Shakespeare and had made humans little lower than the angels, was not an entity, but a connection. It was an open loop that ran between Glockner's Isthmus and the site of episodic memory. It was fragile; it was, in evolutionary terms, very young."
That this Nobel prize-worthy breakthrough comes as an anti-climax, even to the two women who make it, is surely one reason why Faulks became a writer and not a scientist. The 59-year-old author of a dozen books passionately believes that, even in the 21st century, we need literature as well as science to explain things – not least ourselves: "I don't know how you can understand other people or yourself if you haven't read a lot of books," he says. "I just don't think you're equipped to deal with the demands and decisions of life, particularly in your dealings with other people. If I hadn't read all of Jane Austen and DH Lawrence, Tolstoy and Proust, as well as the more fun stuff, I wouldn't know how to break bad news, how to sympathise, how to be a friend or a lover, because I wouldn't have any idea what was going on in anybody else's mind."
A Possible Life, offers up five very different accounts of what it means to be a person. Geoffrey is a prep school teacher, then a spy in wartime France, who is betrayed to the Germans and experiences unimaginable horror shovelling corpses in a death camp. Billy grows up in a Victorian workhouse and makes a go of a life that becomes unexpectedly complicated when his wife recovers from a long illness after he has set up house with her sister. Elena is the lonely neuroscientist who can't quite believe what her own research tells her, and whose childhood memories seem far more pertinent than the shiny new neural pathways revealed by the brain scanner. Jeanne is a poorly educated and pious French family servant in the 1820s, while Anya is a hard-to-resist fantasy – part sexual, part musical — of 70s California. But do these five pieces, varying in length from 30 to 100 pages and with only minor circumstantial connections to one another, really add up to a novel?
"I think it's a novel, I'm sure it's a novel because it's conceived as such and because it is unified," Faulks replies. "The novel is a robust form, and you can do anything you like with it. People have stretched it further than this. BS Johnson famously said you could read the chapters of one of his novels [The Unfortunates] in any order you like. Lots of people have tried this broken-up-sections thing, so there's nothing really new in it, although it is new for me."
Faulks says what interests him most in fiction – more than form, style or plot – is theme. And there is an overarching theme, he says, that holds A Possible Life together: "All my books are about one major idea and two or three subsidiary ones. I have thought a lot about music when constructing books and I like the way in music that themes come back. I find that structure appealing – though I'm not hugely musical and don't want to pretend I am – so I thought it would be interesting to write a novel with four or five separate movements or parts.
"All the sections of this book are about the same thing. They're about identity and the question of our consciousness, and whether death is a proper termination, and whether we're destined to return in some shape or another."
Readers looking for answers to these questions will, however, be disappointed. Faulks's title to the central section, about the scientist Elena Duranti, "Everything Can Be Explained", could hardly be more ironic. On the contrary, as the story wraps up in 2069 with the character sinking into her giant sofa in her futuristic Turin apartment with a glass of wine, he writes: "Elena admits that after a lifetime of scientific research she understands nothing at all."
Among novelists, as he is quick to acknowledge, Faulks occupies a privileged position. "I always thought I would have to have a day job," he says with a laugh and a rap on the wood of the coffee table in the London hotel where we are talking. "When I started out, it wasn't thought you could make a living out of serious or literary fiction unless you got lucky with some big prize." A former journalist who took voluntary redundancy in his late 30s, Faulks has achieved a level of commercial success that must make him a target of envy at many literary gatherings. Birdsong, the novel he wrote straight after switching to writing full-time, published in 1993 when he was 40, has sold more than 3m copies.
Sales figures, often an awkward subject with authors who claim not to know the numbers, trip off his tongue and form part of our conversation. So I learn that Charlotte Gray, his second world war novel which was made into a film starring Cate Blanchett, has sold more than 1m copies. Human Traces, his own favourite among his books and a dense 800 pages of fictionalised history of psychiatry, has sold half a million – five times more than his well-received James Bond continuation Devil May Care.
Next year Birdsong, which was televised this year by the BBC with a screenplay by Abi Morgan, will have its 20th anniversary. Ignored when it came out by the literary prize judges but now studied at A level and one of the outstanding word-of-mouth successes of its decade (Captain Corelli's Mandolin was another), this is the book that defined Faulks's subsequent career. "It was a wonderful thing for me, a completely wonderful thing. And if when I die people say 'that was his big book', then fine. I don't think it's the best book I've written, but to use an analogy, if you have a train with several coaches then it's no bad thing to have a locomotive. Birdsong has pushed or pulled my other books along with it and it is a book that I'm proud of."
The novel describes in visceral detail the experience of trench warfare, including the carnage of the battle of the Somme, and juxtaposes the physical agonies of battle with the sensual delight of a passionate love affair that took place in the same part of France a few years before. Faulks has explained, most recently to the Guardian book club, how the whole era seemed "remote, repulsive and badly memorialised" when he decided to write about it: his own interest was piqued when he was asked to read out a list of old boys killed in the war at a Remembrance Day school assembly, and subsequently lost his voice, a symptom he attributes to shock.
He was not the only author drawn to the first world war as living memories of it began to fade. Pat Barker's Regeneration, the first in a trilogy of war novels, was published two years before Birdsong. The two authors share an agent in Gillon Aitken, but Aitken (having sold Barker's book to Penguin, and Faulks's to Random House) didn't mention the coincidence: Faulks says the first he heard of Barker's book was when he made a trip to the old military hospital at Craiglockhart, where Siegfried Sassoon and Wilfred Owen were treated, and somebody there told him about it.
When Faulks finally met Barker at the Cheltenham festival, "she said a funny thing: 'people think we must be like Coe and Ovett, but I'm delighted [for you].' Actually I think it was mutually helpful. It's like that thing with Italian restaurants. If you have one on a street and another one opens it can be good for business."
Faulks dines out on the tale of how, when he told his editor he was going to write a first world war novel, she was appalled, and clearly enjoys the irony. Since then he has been further emboldened by success to follow his instincts, however far they appear to diverge from trade wisdom. He has written six novels since Birdsong (including A Possible Life), with interruptions along the way for assorted projects such as an admired triple biography, The Fatal Englishman, a book of pastiches pulled together from his days as a radio quiz team captain, and most recently the BBC television series and accompanying book Faulks on Fiction.
Faulks grew up in Newbury, Berkshire, the younger of two sons. His father was a solicitor, his mother worked for the cosmetics company Elizabeth Arden. When he was 10 she had a breakdown, and although she got better, the experience of psychic disarray made a powerful impression. Mental illness is one of Faulks's central themes, most notably in Human Traces, and he has had periods of acute unhappiness himself, starting during his adolescence at Wellington College and continuing into his student years at Cambridge, fictionalised to stark effect in his unusual 1970s murder mystery Engleby.
After university he found a comfortable berth for himself writing features for the Sunday Telegraph, and then moved to the Independent where he met his wife Veronica, with whom he has three children. They live in a house in west London. His elder brother Edward is a Tory peer and a QC, while his sister-in-law is a Conservative councillor. His own politics are harder to pin down. His 2009 state-of-the-nation satire, A Week in December, combines an energetic assault on the venality of hedge fund managers with a swipe at comprehensive education. It also includes strong criticism of Islamic religious teachings, which Faulks amplified when he described the Qu'ran to a newspaper as "the depressive rantings of a schizophrenic" with "no ethical dimension". He later issued an apology.
"The things that make anyone want to be a writer, in your teens when you first get fired up, are always going to be liberal feelings. You're always going to be on the side of the underdog, the individual who is being crushed. Think of the books you read – Jane Eyre, David Copperfield, George Orwell. I've by and large had liberal instincts but that's about as far as I could define myself politically."
But whatever his private preoccupations, Faulks is always mindful of the reader. He is a good plotter who works hard at making it difficult to put his books down: the climactic scene of Birdsong, in which Stephen Wraysford is trapped underground for several days in a tunnel and emerges in a German trench to find the armistice has been signed, provides a cathartic release towards the close of a novel that was always going to struggle to find a happy ending.
For all its horror – and Faulks deserves credit for popularising rage at the catastrophe of the western front – war offers an abundance of life-or-death moments that readers cannot help but find exciting, even as they are regretting the appalling waste of life.
Faulks's father survived the evacuation of Dunkirk, fought in north Africa and Italy and ended the second world war a major. Faulks himself thinks "most people would be interested to find out" how they would have coped had history placed them in the firing line. "I think at the age of 18 I'd have been OK, at 25 I was such a bundle of neuroses that I probably wouldn't have been, at 40 I'd have been OK again. But I do think the generation that fought the second world war was very remarkable, both the men and the women. And I don't think my generation could have done such a good job. That may sound a bit sentimental, but you still sometimes see these guys talking – there was a thing about Bomber Command on television the other day, and they were just so great."
His novels tend to come with generous helpings of sex, though he firmly rejects the idea that there's a valid distinction between fiction that is erotic (good) and pornographic (bad). He cut a graphic scene out of his Bond book in favour of the Flemingesque "he tore her dress roughly and …". "I don't think you should be trying to arouse the reader," he says. "You have to ask yourself, do they need to know?"
In 1998 he won the Literary Review's Bad Sex award for Charlotte Gray – and was so annoyed that he became the first winner not to turn up to the ceremony. But this didn't put him off, and the 1970s California section of his new novel offers explicit details of lovemaking because, in the narrator's words, "what was communicated through sex was more than a coupling; it was the powerhouse of everything between us."
He cites Penelope Fitzgerald along with Alan Hollinghurst and Martin Amis as novelists whose work he admires, but Fitzgerald didn't appear on the list of 28 books featured in Faulks on Fiction. Neither did other women writers, including George Eliot and Virginia Woolf, leading some critics to complain that his version of English literature was too narrow and too male.
Faulks says the whole TV experience was "bruising, very boring". Filming was dogged by bad weather, and the BBC lost confidence in the whole concept of a books programme at several points along the way. No surprise, then, that the final product lacked a convincing argument and over-emphasised one of Faulks's bugbears at the time: the modern propensity to imagine that fictional characters must be based on real people (Faulks had recently fallen victim to a bout of such speculation when rumours circulated that one of the characters in A Week in December was modelled on the writer and critic DJ Taylor).
His next project will be another crack at the state-of-the-nation book he feels he didn't quite nail before: "I really do want to write about this world again. A Week in December ended up being heavily satirical, and humorous, I think, but I didn't set out to write it like that. I wanted to write a much more straightforward, realistic book."
Readers should be warned that his may be a snapshot of the 21st century in which the digital dimension is missing: Faulks believes his three children's lives have been "blighted by electronic media" and could hardly be more scathing in his assessment of Facebook ("nonsense") and Twitter ("just ridiculous, the tweets one reads quoted in newspapers are beneath fatuous").
Whether he can match the pitch and seriousness of Birdsong in a novel set in the 21st century or satisfy his own ambition to do "something more in the line of Roth or Bellow or Updike" remains to be seen. But there's no doubt that he will do his best to entertain as well as inform his readers: "I think there is a transaction. I've always tried to ask quite a lot of the reader, but if you're going to ask a lot then you have to give quite a lot back. It is a contract, a deal. I've probably read 12,000 books, I've written 12, and you know as a reader the point at which you say 'you're not really giving me enough here'. Reading a book is an investment of money if you buy it and certainly of time, and I think you have to honour that.
"My ideal relationship with the reader is that at certain points they will have said 'I'm finding this quite tough but I'm going to hang in there', then at the end they will say 'oh God, I'm glad I hung on, it was so worth it'."
• This article was amended on 18 September 2012. The original referred to Faulks as a former radio quiz host rather than team captain, and has been corrected.
