SEX, SEX, sex - that's all Ewan Morrison thinks about. Well, perhaps not quite all, but that's the impression you'd get if you skimmed through his work and took seriously the title of his blog: "Scottish purveyor of erudite filth", a soubriquet bestowed upon him by Arena magazine. Morrison's debut novel, Swung - about wife-swapping in Glasgow, or swinging as it is known these days - will do little to change the minds of those who regard him as a pornographer, albeit one more interested in exercising brain than groin. Yet this man is regarded by some as the most brilliant emerging talent in Scottish fiction. "All the sex scenes I write have some sense of insecurity or vulnerability in them," he explains. "It's rarely just people getting their kit off and having a great time. That would bore me senseless."

Morrison lives in a tenement in the west end of Glasgow. He has spent the morning discussing with the director David Mackenzie (Young Adam, The Last Great Wilderness) the planned cinema adaptation of Swung. While writing the novel, Morrison did plenty of "field research". He spent 12 months participating in the Glasgow swinging scene - "A Year In Perverse" as he jokingly calls it.

He has longish hair, a scraggle of beard and a black T-shirt bearing these words: I Too Have Sinned. Fuelled by tea and a Marlboro Menthol, he lays out his confession. It all started in 2004 when the film he was trying to direct in New York fell through - "Every aspect of my life collapsed: career, income, personal life" - and he found himself back in Glasgow without a job or a partner. He felt desperate, and on some subconscious level this thought occurred: "You can maybe compensate for the failure you feel in the outside world by doing something different and incredible in your sex life."

Morrison started visiting dating websites. He met an adventurous woman - Joanne - and the two of them started swinging together. He estimates there are around 400 committed couples on the scene in Scotland, and about 6000 others curious to give it a go without making it an important part of their lifestyle.

For Morrison, it went like this. Logging on to swinging websites, he and Joanne emailed other couples and swapped sexually explicit photographs, then mobile numbers. They arranged to meet couples in public places, and if there was mutual attraction they would go to one of their homes and have sex. The women would have sex with each of the men, and on the first occasion they did this, Joanne also had sex with the other woman. Morrison found it fun at first - "It was like being a teenager again. It made sex interesting again" - but then began to have doubts.

"Swinging in a couple actually requires a level of trust and commitment which is probably stronger than that which a normal monogamous couple would have," he explains. "Because what you are doing is containing infidelity on a weekly basis. And there's the potential of coming across people who are more attractive and interesting than you are, who could threaten the relationship that you have. So you've got to have a huge amount of trust and love to be able to sustain that.

"I didn't feel that was there within the swinging partnership I had, so I tried some others but ultimately I came to the conclusion that you should be doing it with someone you love incredibly and it's an extension of your feeling for each other. Otherwise it's just variety for its own sake, and has the danger of becoming an addictive behaviour that is simply postponing the lack of real contact and communication between you."

Morrison also came to realise that he was in fact quite a conventional man who felt rather uptight about inviting strangers into his home and then having sex with them. This was surprising because he'd always considered himself to be "a bit of a perv, basically". Here was a man who had studied feminist film theory at Glasgow School of Art principally as a means of curing his porn addiction (it didn't work) and now he discovered that intense sex with strangers wasn't as enjoyable as having a glass of wine with friends and discussing the relative merits of Dvorak and Mahler. Did he feel let down that he wasn't as extreme an individual as he had thought?

"No, because the main thing is that I put myself in a situation where there are elements of terror and facing the unknown and I came through laughing at the end of it and more in touch with what I can withstand. To set myself a challenge like that, to be drawn into it, to lose control and come out without scars has made me stronger. Most swingers that I know are extremely self-confident and open-minded people. I'd recommend it."

It has been almost two years since he stopped swinging, and he is now in a monogamous relationship. How has the experience affected the way he relates to his partner?

"Well, the focus for me now is very much love. Having taken sex to its limits, I know that you can detach sex from love and it can become a form of entertainment. But ultimately putting sex and love together with a person is a very simple and beautiful thing. Love and mutual care are the things that are of great importance to me now."

Midway through the swinging experience, Morrison began work on Swung. David is a human resources manager for a TV company based in Glasgow. He is separated from his wife and child and has just moved in with a young American woman called Alice. However, his sexual impotence complicates their relationship and leads them to visit swinging sites. Impotence is something Morrison also wrote about in his short story collection, The Last Book You Read. "I've suffered from sexual impotence on only three occasions but for about 25 years I've felt impotent in every other aspect of my life," he says.

He's getting at the contemporary condition of feeling unable to bring about change in society - for instance, a war goes ahead despite massive public will for it not to happen - but also the feeling that we are not fully in control of our own lives. We hate our jobs but stick them out in order to buy the things advertisers tell us we ought to have. Our relationships aren't working but we don't know how to fix them. We aren't the people we want to be.

Morrison's big subject is failure. "I would hate to write a story about someone who set goals and achieved them. That's a very oppressive story and nothing to do with the way most of us live." He is 38 and "very much a part of the Gen X mindset that art and culture can liberate you from the mundanity of your all too predictable life. For my generation, artistic self-expression was high on the list of things that would make life worth living. But generally most of us failed to do that. I know so many people who feel they have failed. We are a massively deluded generation. We all wanted to be pop stars, indie film-makers, poets, painters, conceptual artists. Out of 300 people I know, who I have grown up with, there are four who have managed to do that. It seems crazy that that means there are 276 people who are living a life of resentment. We have a set of unrealistic expectations about sustaining a creative life in the midst of a consumer culture."

Morrison took in unrealistic expectations with his mother's milk. He and his younger sister Glenna, now an actress, grew up in the 1970s in Wick in the far north of Scotland. His parents, David and Edna, were librarians who, in 1965, had moved from Glasgow to Caithness in a Volkswagen Beetle, full of utopian dreams. "There was a bunch of local art teachers, some writers, basically hippies and beatniks, living in the middle of a very downtrodden working-class environment in a total vacuum," Morrison recalls. "This was the gang that I was surrounded by. Ninety-nine percent of them failed and have ended up divorced, separated, alcoholic. Some of them met early deaths."

For Morrison, Wick was an isolating and fearful place to grow up. "Me and my sister were systematically beaten by the locals for about three years. We developed very different ideas about working-class consciousness to the Marxist ideas that my dad was putting forward about the masses rising up and being a liberatory force. I saw the masses as a bunch of kids who wore American sneakers and kicked the shit out of me."

Why did they hate him? "Just because we were hippies. We were long-hairs and wore ridiculous clothes and our parents had nude pictures on the walls. People used to stop and look in our window at the abstract nude paintings."

For seven years in the 1970s and 1980s, David Morrison ran the Wick Festival of Poetry, Folk and Jazz. "They were bringing culture to the masses, but the masses didn't want anything to do with it," his son recalls. On one occasion, he says, three people turned up to see Norman MacCaig read poetry, while 2000 locals opted instead for a performance by The Krankies. Not long after that the family home was repossessed. "So I grew up watching the decline of my parents' ideals and the human damage that came of that."

Morrison doesn't want to be too specific about that damage, but says that failure hit his father very hard and that he witnessed it happen. "It was a huge influence and probably why failure is such a big issue for me."

One of Morrison's best short stories, The Speech, is a largely autobiographical piece in which a son agonises about being fated to repeat the failures of his father. When Morrison lost his job in America and was reduced to selling his possessions in front of his apartment, he had the horrible feeling that that was exactly what was happening. "But it was hugely cathartic to fail on a level comparable to that of my dad because after that I forgave him."

The failure of his own personal American dream, the end of an upward career trajectory in television that had seen him nominated for four Baftas, turned out to be a crucial moment in his new life as a writer. "On the one hand it was a mid-life crisis happening early. On the other hand it was a huge relief to let go. It put me in a better position to be able to write about the aspirational lifestyle as a kind of trap."

Like Joyce leaving Ireland to be able to write about his native land, Morrison is now in self-imposed exile from the middle classes. "There was a time in my life when I had a collection of Le Creuset pans and a Smeg oven, but that's a hard thing to sustain. I quite like the fact that I found my fridge in the street." He taps the table. "I found this on the street as well. What else? That stereo. My telly. My video. I'm a recycler."

He is certainly adept at recycling the events of his own life as fiction. At the start of the interview, I asked Morrison about the experience of writing such a bleak novel. Certain passages were incredibly hard for him - he was in tears - and they tended to be focused on children. Morrison has two children from a previous relationship, and it's surely significant that in his writing - Swung and the longish piece The Undoing Of A Story - the only moments of possible redemption are to do with a father's love for his children, and in the case of The Speech, a man's love for his father. "Making lives and giving love in the shaping of lives is maybe all life is really about," he says, "and all the other ambitions fall by the wayside in comparison. The kind of love you give a child is the kind of love that is worthwhile. That's the way I see the world. I don't think there are many other goals worth fighting for."

Over the course of one year, Morrison showed every part of his body to strangers, and more recently his well-endowed mind to the reading public. It's nice to finally get a glimpse of his heart too.

Swung is published by Jonathan Cape on April 19. Ewan Morrison will be at Waterstone's, Princes Street, Edinburgh, at 6pm that evening. At 6.30pm on May 10, he will be at Waterstone's, Sauchiehall Street, Glasgow