Colm Tóibín has an extraordinary head. It looks as if it was sculpted by someone with enormous powers of expression, but fairly rudimentary chisel skills. In photographs, he can look stern, brooding. In the flesh, though, there’s a sprightliness to him, a mischief. People who know him talk about how he lights up a room with his presence.

As he sits in an armchair in his house in Dublin, he hugs his chest and emits squawks of delighted laughter. This is after I’ve told him that a friend of mine - a woman - said that she found the sex scenes in his novel Brooklyn, winner of the Best Novel category in this year’s Costa Book Awards, entirely convincing “from a woman’s point of view”. Nothing especially odd about this - except that Tóibín is gay and had, he says, to do a certain amount of boning up beforehand.

“I asked this woman friend a crucial question: ‘What’s it like this first time?’ And she gave me this - this very graphic account of how it felt and I found that very useful. Once I’d got that, it wasn’t too hard.” Tóibín goes on to point out that the two best accounts of gay sex that he’s read - in Annie Proulx’s Brokeback Mountain and Pat Barker’s The Eye in the Door - were both written by heterosexuals.

Lest anyone should assume that Brooklyn is one long rollicking flesh-fest, it’s worth pointing out that this could hardly be wider of the mark. The novel is an account of what happens to Eilis Lacey, a young Irish woman, when she leaves Ireland in the early Fifties and goes to work in New York. It’s a delicately wrought, deeply affecting book that sees Eilis’s heart being tugged first one way and then another.

The spark that eventually ignited it came from a childhood memory of Tóibín’s. His father died when he was 12 and among the visitors who came to pay their respects to his mother was a woman whose daughter had gone to Brooklyn and got married. “For some reason the incident made a big impression on me. I remember the woman - her scarves and her hat and so on - and I remember her talking about her daughter and how much they were going to miss her.” Tóibín originally wrote a short story in which this woman appeared, briefly, 10 years ago. “There were just a few sentences, nothing more.” He then put the story aside with a vague sense that there might be more to be done with it.

Five years later, he picked it up again. In the intervening years, Tóibín had spent a lot of time travelling back and forth to the United States: he’s been a visiting professor of creative writing at Stanford, the University of Texas and at Princeton. He’d also been teaching a lot of Jane Austen. Both these things were to prove crucial - both to the story of Brooklyn and to the way he told it.

“I reread the short story one night and there it was, the story of the woman who’d gone to Brooklyn. The minute I saw it, I thought: ‘There’s something there.’ Straightaway, I realised what I could do with it - which had never occurred to me when I wrote the story.” Right from the start, Tóibín was determined that this would be a book without any detectable style to it: the story would unfold in the plainest possible way. “I wanted to cut everything right back. Part of that was as an experiment: I was hoping that if you got the level of detail right then the reader would slowly become emotionally involved without knowing at what point that began. It also went back to the teaching I’d done. I’d spent a lot of time at Stanford talking to students about stories that were nearly there, but not quite. How much should you tell a reader? How much should you withhold? All that sort of stuff.

“Here,” he says, “I’ll show you what I mean ...” Tóibín proceeds to demonstrate what makes him such a good writer - and also, you suspect, an inspiring teacher. “For instance, you could write a sentence like: ‘He hated his mother more in that moment than he had ever hated her before.’ But, alternatively, you could say: ‘When his mother turned away from him, he looked out and he noticed that the branches of the tree were swaying. He held his eyes on it for a moment, and when he looked back she was staring at him.’ See? It doesn’t really matter who hates who anymore, but something has occurred. There’s something there that makes the reader shiver. All writing is a form of manipulation, of course, but you realise that a plain sentence can actually do so much.”

All of Tóibín’s six novels are about people who are walled-up in some way, cut off from their emotions. They try to hide themselves from the public gaze, to keep their secrets concealed. His last novel, The Master, which was narrowly pipped to the Man Booker prize by Alan Hollinghurst in 2004, was a fictionalised account of the life of Henry James, a man who could only allow himself to engage with feelings through his fiction.

I wondered how much, if any, of this fascination with concealment was a result of his growing up gay in Sixties Ireland. Tóibín, now 54, tilts forward in his armchair and thinks for quite a long time before he speaks.

“I don’t think it does, no,” he says. “In fact, a few years ago, I realised I had missed the point. Between the time I was 16 until I was about 20, the books I read were by people like Thomas Mann, James Baldwin, Thom Gunn, Elizabeth Bishop. All gay, of course, although I swear I didn’t know that at the time. Yet all of them, it turned out, had had a parent who died during their childhood. Sexuality is nothing compared to that. It’s an issue that affects and unites people much more than whether they’re gay or straight. Whoever you are, it hits you very hard and I’ve never known anyone to recover from it.”

Tóibín was 12 when he started writing - the same age he was when his father, a teacher, died. “I mean, clearly there’s a connection, but it’s terribly difficult to analyse yourself and most people shouldn’t. Certainly I don’t think novelists should, on the basis that the less you know about yourself, the more likely you are to use those useful bits that are sort-of hidden from you.”

But I read somewhere that you see a therapist regularly?

Tóibín gives another squawk of laughter. “Of course, I do! Of course I see a therapist!”

Isn’t there a little bit of a contradiction there? “Well, in fact, the therapist is a really good friend. I don’t think we’ve done an actual session for years, but we talk a lot, and have supper and go to concerts. So I see a therapist socially, put it that way.”

Tóibín gets up and pours us both another glass of wine. Moving around the room in a long, shapeless grey sweater, there’s something engagingly bearish about him - an impression partially offset by the bright red reading glasses he wears strung round his neck. All around, on his desk, the shelves and on the floor, are piles of books. While his surroundings may not necessarily suggest it, he is a man who leads what he describes as a “very regular life”. Or at least he does when he’s in Dublin. When he’s in the US, his life is rather less ordered.

“In fact, I’ve had to stop drinking when I’m in New York because I couldn’t deal with the hangovers. There’s also something funny about the wine there. They have this stuff called” - he wrinkles his face in disgust - “pinot grigio.” Recently, Tóibín has also built himself a house overlooking the sea in County Wexford, close to where he was brought up. “It’s perfect in every way and when I’m away it fills my dreams. When I’m there, though, I find I can concentrate really well for about four days and then I get restless again.”

Despite all this hopping about, he’s managed to be extremely productive: not only six novels, but also three travel books, a biography, a collection of essays, a play, a collection of short stories - as well as regular pieces for the London Review of Books and the New York Review of Books.

“I did a reading at Trinity College a few years ago and the deal was that the students buy all your books, then you sign them and they put them in a glass case. I remember seeing all these books there and feeling ... almost fear. Almost shrinking from them, as if it was much more than I had in mind, more than I planned.”

 Do you have a sense of pride when you finish a book?
 He shakes his head. “None.”
 Really?

“When a book comes from the publisher and you see it for the first time ... Of course it’s not remotely like seeing a baby for the first time, but I can remember with each book what room I was in when I opened it. That would be excitement, though, I think. Not pride.”

There is, plainly, a contrast between the melancholy tone of Tóibín’s writing and the ebullience of his personality. “Mmm ... I noticed it first when my second novel [The Heather Blazing] came out. A number of people said to me: ‘Did you really write that book?’ It made no sense to anyone - except to those people who knew me very well. In fact, I have a friend who’s always saying to me: ‘Colm, why don’t you write a funny book?’ And I always say to him: ‘Every time I do, it just turns out really sad.’?”

Does that bother him at all? He shakes his head again, less gloomily this time. “I suppose one should have an integrated personality,” he says, “but I’ve never really seen the point.”