Iain Banks looks on the bright side of dystopia with his 'hybrid' book

For 25 years, Iain Banks has been penning literary novels and science fiction under two names. Now, for the first time, he has combined the two.

When Iain Banks closes his eyes to dream of an alternative universe in which he is his own, all-conquering hero, he sees two scenarios: "The first one has someone saying 'Congratulations, Mr Banks. You've won the Pulitzer prize," says Banks, with a chuckle. "In the other, someone says 'Please welcome the conductor, Mr Banks, to the Proms'."

With a prodigious output of 24 books published since his sensational debut in 1984, The Wasp Factory, and a new book freshly delivered to his vast army of fans this month, the first flight of fantasy is not beyond the bounds of possibility. The second, he admits, is rather more exotic, but he's laying down the foundations nonetheless, with two piano lessons under his belt and a faltering rendition of "Chopsticks" to boot. This, he hopes, will eventually culminate in the composition of his first full-scale symphony ("I'm a sucker for a good tune, anything you can whistle") created on the same computer on which he writes books and plays games, over the next four months.

"I'm not suggesting it will become a second revenue stream, but I love doing it. It's very much like writing a novel: there are different themes, individual melodies and threads that appear and interact with other melodies, just like characters. And it is linear in that there is a beginning, middle and end."

As far as endings go, Banks has had his fair share of late, some of which have been happier than others. He recently finished writing Transition (Little, Brown £18.99), a science-fiction romp-cum thriller which marks the merger of his two long-standing literary identities: Iain Banks (who pens brooding literary fiction) and Iain M Banks (who scribbles SF adventures filled with spaceships and shape-shifters).

The parallel universe in Transition is very different to the "Culture", the benevolent universe in which nearly everyone is happy, that re-emerges in his SF work time and again. Here, we have the Concern, a darker, more malevolent intergalactic organisation whose leaders have learnt to invade bodies and travel through time. At its head stands Madame d'Ortolan, an evil genius who commandeers psychopathic assassins to carry out her will. An array of colourful characters, including the action hero, Temudjin Oh, and the sultry Mrs Milverhill, cross paths, time zones and locations to bring the story to a hair-raising showdown.

The backdrop to the book is the "peaceful" interregnum between the fall of the Berlin Wall and the collapse of the Twin Towers, a world of carefree conspicuous consumption not yet hit by economic disaster and described by Banks's publishers as one that "hangs suspended between triumph and catastrophe... frozen in the shadow of suicide terrorism and global financial collapse."

So it is interesting that Banks choose to put terrorism – and Christian terrorism at that - at the heart of the plot. Was it an attempt at prescience, an exercise in spotting the approach of a terrorist atrocity, preceded by extremist rhetoric and as yet unvented rage?

"Well, it (the 1990s) was a world in which we didn't realised we were living through a golden age. The very real threat of nuclear war had lifted. There was a false threat of terrorism. I wanted to explore that theme and what might be coming next.

"I thought [Christianity] was a great religion for terrorists. You can do anything as long as you confess, in Catholicism anyway. And together with the idea of 'original sin', Christianity seems to have a better set-up for terrorism than Islam. It would have been too easy to do Islamic terrorism," he says.

What makes it more ambitious is Banks's endeavour to make the strands of the book as multifarious or as "symphonic" as possible, perhaps to showcase his talents as SF master to his mainstream fiction fanbase.

"Writing can be compared to Olympic diving," he says. "You can have a beautifully executed but very simple dive which will win you the gold medal, or you can have a really complicated twisting somersaulting dive and win the gold for complexity. If you want to push your writing on, you can't spend all your time doing the easy stuff. You have to make it more complicated. I was quite consciously making this one complicated. It's a show-off piece which says 'look what I can do'. I just thought it was time to do that again."

The template for the book was his third novel, The Bridge, which had fantasy elements but was catalogued under his "mainstream" oeuvre.

"It was reviewed as science fiction but I considered it to be mainstream. In the last few mainstream novels, much as I enjoyed writing them, I felt more interested in doing something like The Bridge, with more story strands."

Aside from the book, another ending this year, more tragically, was the death of his father, Robert Banks, in June. This happened around the same time as his divorce papers came through, ending a relationship of over 20 years. Just as he was contending with those immense losses, his mother fell and wound up in hospital, though he is hopeful of her recovery – "she's an ex-professional ice skater so she knows how to fall."

His father's death at the age of 91, his mother's injury, the end of a marriage and its protracted break-up, has put him in reflective mood.

"My father was a friend and I miss him. The writing probably comes from his side. He was always known as a good letter writer. His death came around the same time as the papers for my divorce came through. I spoke to a friend about it, and he said 'you're just at that age'. I count myself lucky to have had my parents close by. I've always lived near."

With the gut-wrenching endings have come some new, rather surprising beginnings too. He has a new passport (he tore up his old one as a protest against the Iraq war and resolved not to get another one until Tony Blair left office), a new relationship (his girlfriend is the author Adele Hartley), a budding musical ambition and, most unpredictably of all, a new spirit of restraint for a writer who has written some of his works with rock music hammering in the background and revelled in his love of whisky, aeroplanes, motorbikes and the high-speed cars in which he has bombed around the Scottish shires for half his life.

Now sitting in the Assembly Rooms in Edinburgh, where he has just finished discussing his double life as a science-fiction writer and a literary novelist with Clive James as part of the city's book fair, Banks looks leaner than he has for years, in jogging shoes and hiker's jacket. His carbon footprint has shrunk likewise: he has sold off his five sports cars (a Jaguar, two Porsches, BMW and Land Rover) and swapped them for something greener. He has not flown on an aeroplane since 2005 and he now takes his whisky - once the subject of Raw Spirit, a book which took him carousing across Scotland - in moderate tipples.

Banks underplays the irony of cleaning up in mid-life, around the same time that many men his age (of 55) might consider acquiring their first pair of leather trousers and a Porsche, but he does speak wistfully about his fast-living days of yore.

"I miss the cars a lot. I finally cracked and bought a Mini soft top because it's green and it's got the smallest engine. The other thing I miss is flying. I was learning to fly and I wasn't far off sitting my test. I was doing cross-country roving exercises and I had done 45 hours. I miss it a lot. The scariest – and the best bit – was coming in to land. The take off is optional; the landing is mandatory...I have dreams about it."

Banks grew up as an only child in Fife, in a house that was bursting with books, which he quickly learned to love. "The house was filled with books. I remember being absolutely stunned when I went back to one of my pal's homes and there were no books in the house. For me, it was like discovering that they didn't have any running water or electricity."

His parents encouraged him to develop a rich fantasy life and he found science fiction to be the best outlet. "With science fiction, I could really unleash my imagination and there was a degree of wish fulfilment. I believe in wish fulfilment now, you shouldn't denigrate it."

Banks's inherent optimism comes as some surprise, given the dark, sometimes perverse nature of his literary fiction over the years – from the sadistic animal-torturing protagonist in The Wasp Factory to the maniacal desires of the serial killer in Complicity and the preoccupations with death, sex and drink in The Crow Road - but he regards this as proof that he really is creating fiction rather than veering into barely-fictionalised autobiography that airs unresolved demons.

His desire to create dark worlds is partly based on pragmatism - "It's great being a happy person but nobody wants to read about one. Dystopias are more exciting". But interestingly, his science fiction was inspired from a wish to bring some light into the genre, namely through his creation of the Culture – a land of plenty in which poverty has been abolished.

"I began writing in response to all that dark stuff. I thought dystopias were over-represented in the future. What no one was saying was that the future might not kill us. It might be fabulous fun. It's may be a childish thing in a way. A large part of science fiction is this fantasy, or make-believe, for me," he reflects.

So what of the "M" now? Having written both as Iain Banks and Iain M Banks since 1987, there have been rumblings that Banks has, with Transition, integrated this schizophrenic literary persona. "No, the 'M' stays," he answers. "I get something out of writing in two genres, a kick that I have got away with writing both..."

Once the symphony is done and dusted, he plans to start on his next science fiction novel, complete with laser guns and spaceships, he says, followed by a book that will be "as visceral as The Wasp Factory.

So braced with unleashing another tide of darkness, Banks picks up his napsnack and bounces off, Tigger-like, to meet his girlfriend for a curry, the cheery master of doom and gloom.

* Arifa Akbar travelled to Edinburgh by train with National Express East Coast ( www.nationalexpresseastcoast.com )