`When I was about 10 I decided I'd be a writer. It seemed like a good idea." Twenty-two years - and many unpublished poems and short stories later - Keith Ridgway's ambitions are being realised with the publication of his first novel by Faber. Much of the advance publicity around The Long Falling has focused on the fact that it is set during the infamous X case in 1992. But the novel is more truly about Grace, an Englishwoman living on the border of Cavan and Monaghan, married to a bullying husband, and their son, Martin, who is gay and has escaped his father's wrath by moving to Dublin.

"The book isn't about abortion. The X case is there in the background," explains Ridgway, a Dubliner who works part-time in the Irish Film Archive. "I'm not using the X case as a plot hook. I would hate people to think that." He has not been interviewed before and finds my questions interesting but a little worrying. "Yes, it's a bleak book. Too bleak, perhaps?" He is not sure whether we should reveal Grace's secret, which unravels as the book progresses and teases the reader who tries to guess her eventual fate: "I'm not sure how much of it to give away." He likes creating the tension of suspense, and (although Dostoevsky and Beckett are his real loves) he is an admirer of Brian Moore's use of "pace and plot". For the moment, we decide not to spill the beans about Grace, and return to the significance of setting her story at the same time as the unfolding of the X case: "I was wondering when to set the novel. I remember thinking at the time of the X case: `Someone is going to have to write about this.' The sense of shock in Dublin then seemed to match the mood of Grace's story."

Grace's name, together with the title of the novel, prefigures her subversion of the traditional Irish expectations of womanhood, a subversion also personified by the 14-year-old at the centre of the X case. The story of these two wronged and defiant women, one the fictional Grace, the other, the real-life X, coalesce in the impressive penultimate scene of the protest march in Dublin: "Somebody in front of them shouted suddenly `Not the church, not the State, women must control their fate,' and others took it up . . . Grace chanted once, almost inaudibly, and then once more, a little louder, and then again, louder still . . . It occurred to her that they would be a formidable sight and a shuddering sound. They would brook no argument."

Ridgway explores the significance of the march, which took place four days before the injunction was lifted by the Supreme Court, allowing X to travel to England for an abortion: "There was a sense that it was a public and political statement, but also a very personal thing for a lot of people, independent of what they thought of abortion. Everyone was traumatised by it."

The X case and the events in the novel illustrate that "although Irish society is more progressive than it was, for individuals in families, things take time to change," believes Ridgway. "It is not that easy for a society to move on and somebody, like Grace, ends up paying the price." The novel began as his attempt to depict "the gay scene in Dublin as I knew it in 1992", including the old Parliament Bar ("gone now") and the sauna scene ("there have been saunas operating here since the 1970s without any real opposition"). Grace's son Martin moves in this world, and introduces his mother to a small part of it when she comes to see him in Dublin. Martin is in a stable partnership with Henry, a three-dimensional, finely nuanced relationship that is depicted brilliantly by Ridgway in all its jealousy, tenderness and need: "I wanted to write about the real nature of gay relationships. They are as frustrating and rewarding as straight ones, and people tend to forget that."

We see the tawdry sauna through Martin's jaded eyes as he goes there late one night, lonely for Henry (who is working temporarily in Paris). Insecure and positive that Henry is being unfaithful, Martin toys with the idea of getting his revenge by having a one-night stand, but is repulsed by the atmosphere of "despair": "They looked like men given some terrible task. They wanted it over with. They wanted it done right . . . Inside [the steam room] there were grey bodies piled in a corner and the smell of poppers was like a gas leak, and almost immediately his cock was in somebody's hand. He pushed him away, tried to get his bearings."

Ridgway found that he didn't like Martin very much (a reaction the reader of The Long Falling will share - not because he is badly drawn; he is simply an unlikeable person), so he hit on the idea of giving Grace the central role in the novel by making her Martin's mother. Grace had earlier been conceived independently of Martin, as the main character in a short story: "The characters who are most removed from me, like women and old people, are the ones who interest me the most."

One of the most memorable figures in the novel, Mrs Talbot, fits this description. A no-nonsense, larger-than-life widow, she runs a boarding-house and takes Grace (alias Mrs Wilson) in at a time when Martin has let her down and she has nowhere else to turn: "She closed the door on her and stuck her hands in her apron and squinted at the morning light coming up from the hall. Wilson. It was a quick name, nothing hung to it. Mrs Talbot stepped to the stairs and eased herself down like the launch of a lifeboat. What class of disaster was this, she wondered."

Ridgway finished a draft of the novel three years ago and gave it to an agent, who tried unsuccessfully to sell it. Ridgway did a rewrite, making it "tighter", and it was snapped up quickly by Faber. Did it help that the main character is English? "I never thought of that. My main concern was that she is English but born of Irish parents. She is Irish enough to get on the football team, but she is still an outsider. I wanted to explore our whole obsession with what it means to be Irish."

He is looking forward to the idea of being recognised as a writer. "I don't know any other writers. I don't move in those circles. I'd go to readings and recognise writers but I wouldn't have got chatting to them before."

He had a short story, Horses, published by Faber in last year's First Fictions 13. He is now working on a new novel, which he describes as "set in present-day Dublin, with a load of characters. It's pacier than The Long Falling. And it's less bleak. I'm fed up with bleak."

The Long Falling is published by Faber on February 16th (£10 in UK).