IAIN BANKS IS, he admits, a 'funny mix': a best-selling author undoubtedly; an obsessive certainly. He nods vigorously, twice. A schizophrenic, perhaps? 'Come on,' he says crossly from behind his refuge of beard, glasses and swatch of tabletop. 'I don't hear voices in my head or anything.' But his is undeniably a split personality - a trait that permeates all that he does, not least his work. He writes mainstream novels as Iain Banks and equally popular science fiction under the pseudonym Iain M Banks. Even his 'regular' titles are split down the middle. 'I write nice and nasty books,' he says, slightly smugly. Banks is an amalgam of contradiction. A real-ale loving, computer game geek with a very unstuffy passion for fast cars, drugs, sex and violence; a self-professed feminist who admits to cheating on his wife with a string of affairs before their marriage. He confesses: 'You do become more attractive as a man when you become more successful. It's hard not to take advantage of that.' Ostensibly open but in reality guarded, he hides behind a bluff of bonhomie and laughter. He is gregarious but, one suspects, always just one step removed - a classic only child. 'I always had friends,' he says. 'But I never shared my life that intimately with children when I was a kid. I'm deeply egocentric.' And, as such, he is not above the occasional prop. He has had his trademark beard since he was 23. 'Strategic laziness,' he claims. 'I only have to trim it once a week.' It is, however, a barrier of sorts. Likewise, it would come as no surprise to learn that he had, in fact, 20-20 vision and that his prescription lenses were actually not needed. But then you should never trust a man with too much imagination. And Banks has it coming out of his ears. This is the writer whose first, million-selling novel, The Wasp Factory - about a bored adolescent who murders three people and then amuses himself by mutilating animals - was printed on his 30th birthday after being rejected by six publishers. One editor famously dismissed it saying: 'Quite well written, but far too weird ever to get published.' The incongruity delights him still. 'Serves the bugger right. I bet he worked for Decca [records] when they knocked back The Beatles.' Since then, he has churned out more than 20 novels in 19 years, a furious pace. It takes him just three months - 'eight hours a day, five days a week' - to write a book. 'I start in October, finish by Christmas, revise over New Year and have it with my editor by February. Then I take the rest of the year off. I'm really a disciplined slacker at heart.' His #250,000-a-year (HK$3.2 million) industry funds a playboy's existence, with a sprawling house in North Queens-ferry, Fife, 'a Porsche, a BMW, a Jag, a Land Rover and a boat'. And his energy is contagious, if unsettling. He drums the table with a percussive intensity, periodically breaking off to slash the air by way of illustration. But he is, at 49, slowing down at last. 'I used to have ideas all the time, jotting them down. Now I don't. I don't have that bubbling I used to have in my 20s. I think I'll probably always write but the frequency will just decrease. That's true of most things in life though, isn't it?' He laughs uproariously, bashing the air, and takes a gulp from his glass of Perrier. Perhaps the lack of ideas inspired his first work of non-fiction, released this week. Raw Power (Century) follows Banks as he tours Scotland's whisky distilleries in search of the perfect dram. He is a man of compulsion and appetite, with an urge to compartmentalise, if not wholly reinvent, his life. A friend told him recently: 'If I earned as much as you, I'd dress better.' So he went out and spent thousands of dollars on designer clothes. But today he is wearing a lumberjack's shirt and #12.99 jeans. 'A few months ago I was wearing this really nice Versace suit, which cost about two grand, and two buttons flew off. I just thought, 'What the hell is this about?' I've been through my designer phase.' So, too, went his year-long unfaithful phase - which came perilously close to breaking up his relationship with Annie, the 'glorious blonde secretary' he met in 1980 at a law firm in London where he was a costings clerk. 'I was fairly awkward with girls,' he says. 'I had difficulty asking them to go to the school dance. But when I met Annie that was it. Bumf.' So was she his first serious girlfriend? 'No, no, no.' He looks affronted. 'I'd had the standard amount.' How many is that then? He looks embarrassed. 'Oh, I don't know. Six or so?' The Wasp Factory was published four years later and he became an overnight phenomenon. A review in The Mail On Sunday said: 'If a nastier, more vicious or distasteful novel appears this spring, I shall be surprised. But there is unlikely to be a better one either.' And the feted author, awash with success, duly embarked on a 'string' of affairs. Banks does nothing by halves. Three years ago he became so addicted to games that he installed his computer in the house next door he had just bought for his parents, so they could police his gaming. And infidelity proved no exception. He crammed 'half-a-dozen' affairs into one year. Then he suddenly stopped, confessed, fought to win Annie back - 'she gave me two years off for bad behaviour' - got married in Hawaii 11 years ago, and has never strayed again. So why did he do it? 'I was an immature 34. If your eyes are inclined to rove, it's a problem. Publishing is full of these beautiful, intelligent and witty women, more than most professions. And those are the sort of women I've always liked.' A year into his marriage, Complicity came out. The story of a dissolute, drug-taking 30-something man who has a torrid, sadomasochistic affair with another man's wife. So is the character autobiographical? Banks looks, just for an instant, as though he wished his glass held whisky rather sparkling water. 'No, that is not me. I'm not particularly a sexual creature. It's not one of my abiding interests. For example, if you had access to my computer you wouldn't find any sex sites on it.' This seems rather unconvincing. Incriminatory even. Did there used to be? 'Actually,' he offers, edgily, 'it's brand new, so there wouldn't be anyway.' He tails off limply before leaping back with evident relief to his world of fiction. 'Complicity is the most sexual of my books, yes. I just wanted to make the guy compulsive in every way. His game playing. His drug taking. His sexual appetite. And I am compulsive, but not in that way. My sexuality is not his. Kinky sex and bondage is just not me. Even when I was writing all that, I was thinking, 'Sex should be fun. This sounds like hard work.' 'I remember being in Belfast around that time. At one of those weird promos these two young lassies came up to me at the signing afterwards. They said, 'We, er, read Complicity. Are you into that then?' 'I was like, 'Christ, not really, no. It's just a story. I'm not into attacking people or murdering them either. It's the character, not me.' But I was definitely getting an offer there. Scary.' Middle-aged, with his gingery and unruly whiskers, snaggly teeth and those own-brand jeans, he is not an obvious pin-up. 'No, literary groupies sadly tend to be very thin on the ground,' he admits, only half-joking. 'I once mentioned this to a couple of women friends. They said, 'We'd have been there for you, Iain.' And I was like, 'Damn, why didn't you mention this five years ago when I was footloose and fancy-free?'' And there's the rub. Despite his bawdy talk and almost nostalgic retelling of affairs, he is irredeemably domesticated now. A natural husband, if surprisingly traditional, chauvinist even, with his horribly antiseptic habit of calling women 'females'. 'Annie does housewifely things, domestic stuff, keeping me supplied with coffee and biscuits and soup for lunchtime. She's not possessive. We don't go through each other pockets or anything. 'She only does that before she puts my trousers in the wash, to make sure there's no tissue paper in them.'' Banks and his wife come from settled, if unconventional, families. Her parents - German mother, English father - met in 1946 in Germany where he was stationed. His parents met on the Dunfermline ice rink, where his mother Jessie, 77, was a professional skater and instructor. His father Tom, 10 years her senior, started in the navy as an able-bodied seaman, but worked his way up to be a first officer in the Admiralty, the government body overseeing the British navy. 'We still lived in council houses,' Banks points out. 'But I'm not claiming to be some horny-handed son of the soil. I was very spoilt. I had the best possible start you can ever get. I just always felt very loved, basically. And nothing ever happened that interfered with that. 'I think that's why, when my imagination starts to go into dodgy areas of sexuality or pain, there's nothing in me that says, 'No, I don't want to go there, I want to shy away from that, because it brings back horrible memories.' I think the imagination is amoral. It'll just go anywhere you let it. But I would argue that my books have a morality. The vast majority of the horrible things that happen to people in my books occur to men.'' Being an only child, he says, gave him a 'thoroughly undeserved' belief that 'everything revolves around me'. And he has clearly never quite thrown that off. Banks adds frankly: 'But I suspect most writers are like that. Especially men. One of the most abiding tragedies is the number of female writers who say, 'I used to write until the children came along.' That's what they end up giving all their time to . . . It's almost an either/or thing. You either have children or you have a writing career. It's very difficult to have both. But for men, it's easier.' Such conflict is, however, destined never to be an issue for Banks. He and his 47-year-old wife cannot have children. 'We didn't plan it that way but it's just not been possible.'' And with that he drains the last few bubbles from his glass, switches the mobile clipped to his hip back on and waits patiently for his wife to call.