Iain Banks doesn't have a passport. In 2003, he ripped it up and sent it to Tony Blair as a protest against the invasion of Iraq. "I'm waiting until the bad man's gone, then I won't feel ashamed to be British," he jokes. The good news, he says, is that it gives him an excuse not to go on book tours abroad.
His publishers might have something to say about that. After a wait of five years, Banks has a new novel out. A sprawling family saga, The Steep Approach to Garbadale is being hailed as his best book in years.
Banks is the Tarantino of the book world. In 1984 he became an overnight sensation when he published The Wasp Factory, the tale of a bored adolescent who murders three people, then amuses himself by mutilating animals. Short, violent and wilfully perverse, it divided the critics and became a cult classic.
Since then he has written more than 20 books, alternating literary novels with science fiction. With paperback print runs of 200,000, he is one of Britain's most successful authors. The Crow Road was adapted for TV starring a young Dougray Scott, while Complicity became a film.
Now 53, Banks still resembles a 1970s polytechnic lecturer, but his wardrobe has improved. "A couple of years ago, my pal Les said, 'If I earned as much as you, I'd dress better'," he admits. "So, now I'm addicted to shopping. This is a bloody Paul Smith shirt I'm wearing here!"
Banks likes to present himself as a bit of a slacker. He can afford to write for three months of the year, then take the next nine off. It has always been important to him to have a life outside writing. His passions include fast cars and computer games. Some critics accuse him of having too much fun. "I never had a guilt-making religious background," he agrees. "I'm lucky to have escaped all that Calvinist nonsense. I think you can live a perfectly moral life as an atheist and a humanist."
An old-style socialist, he still lives in North Queensferry, Fife, where he grew up. "Gordon Brown has a house 100 yards up the road from me. My mum used to sit beside him in the church and I'd say, 'Mum, mum, when you see Gordon next week, tell him to drop the PFI for London Underground, it's stupid.' And she'd say [he mimics a high voice] 'I certainly will not'."
He thinks Brown will make a better PM than Blair. "His hands are relatively clean when it comes to the Iraq war. But he's still very much a monetarist and a privatiser, so I couldn't bring myself to vote for him."
Banks usually votes SNP, but he's heard a rumour that the party will guarantee the Catholic adoption agencies a get-out from the Sexual Orientation Regulations Act. "So I'll probably waste my vote on some extreme leftwing candidate as usual."
Banks is very much New Bloke. It's noticeable that the victims of violent crime in his books are male. "I was reacting against the fact that there are so many books that have violence against women."
Because his work is full of murder, sexual perversion and drug abuse, people assume he had a disturbed childhood, but no, he says, he had incredibly secure, loving parents. "I felt very cherished in every way. And I think that's the single most important thing you can do for a child: just love them."
An only child, he was addicted to reading, but he had an extended network of cousins that inspired the eccentric dynasty in the new novel. His earliest influences came from TV and science fiction. He knew he wanted to be a writer from the age of 11. He was hardly a teenage rebel, but he was obsessed with making bombs out of sugar and weedkiller (on his university application form he cited just one interest: explosives).
Banks studied literature with psychology and philosophy at Stirling University. Afterwards he hitchhiked round Europe and took a series of dead-end jobs. He wrote for 10 years before he was published, pinning the rejection slips over his bedroom wall - The Wasp Factory was rejected six times, then retrieved from the slush pile. Banks has since been voted the fifth greatest writer ever - after Shakespeare, Austen, Orwell and Dickens - in a BBC website poll.
He's never won a major prize, probably because he is unapologetically populist. "I have a weakness for plots and stories and surprise endings." But his books always have a social conscience. Complicity was a "considered comment" on Thatcherism; Dead Air opens with the attacks on the World Trade Center.
Recently, one sensed writing had become a bit of a chore for Banks. But he's hugely proud of The Steep Approach to Garbadale. It follows the Wopuld family (inventors of a Monopoly-style game) from the 1970s to the present. In many ways it is a tale of unrequited love. The hero, Alban, is haunted by a teenage love affair with his cousin.
For the first time, Banks tells me why the new book is late. He and his wife, Ann, have split up after 25 years. "It was quite traumatic. For the first time I had to ask for an extension. It was like being a student again." Looking back, he wonders if his last few books felt slightly laboured "because obviously things weren't going right in my marriage. I didn't feel I was under strain, but clearly I must have been."
The new novel is full of the turbulence of first love. At first he was nervous about writing sex scenes for 14-year-olds. "It almost felt like paedophilia. You think, 'Are you sure about this?' But I think everyone remembers being a teenager quite vividly."
Towards the end of our interview, Banks casually mentions a new girlfriend. Readers might want to look up the character of Verushka - Alban's fortysomething girlfriend - in the new book. Banks says that she is "an elderly male novelist's wish fulfilment".
In the past, critics have argued that Banks's characters lack warmth, but recent life experience has given his writing new depth. "Lots of un-fun things have happened. But my mum and dad are still alive, bless them, at 82 and 88, so I'm not even half an orphan yet. So I'm very lucky."
Do you need to suffer to be a great artist? "I have a suspicion you do," he sighs. "Mind you," he adds brightening, "it would be very difficult to do the controlled experiment. You'd have to take identical twins and make one suffer, and the other one have a life of Riley and see which one produces the better work!"