Life is never easy for characters in a Marina Carr play. "They're ordinary people caught in extreme situations. I've never considered the plays violent, though many people do, and I've always been surprised when I'm told this."

Her new play On Raftery's Hill directed by Garry Hynes and starring Tom Hickey, opens next week at the Town Hall Theatre in Galway. Carr seems quite calm about it all. Through works such as The Mai, Portia Coughlan and By the Bog of Cats, she has evoked the midlands world lying within the precise triangle of Clonmacnoise, Tullamore and Birr, Co Offaly.

The exactness is chilling and authentic. She says: "It's the place I know. But then I haven't lived there since I was 17, so I suppose it's become the midlands of my imagination. But I do remember the way the people speak, that particular rhythm of English as spoken in the midlands."

Language dominates her approach to writing. "You could say in the new play nothing happens except for the cat dying," she remarks. It's not strictly true but she has a point. Her plays are less stories than studies of turmoil as experienced in a precise form of inertia. Much has been made of the rawness of the verbal exchanges.

"It's true that a swear word used in the right place can be very effective but I have become more and more intolerant of strong language; I think it brings a laziness to the writing. I have moved away from it. But anyhow, you come around to thinking less is more. I think when you start out you want all the frills. It's too easy to want to show off what you can do, to show off all the words you know. But that's not important. Writing is not about what you can do - that's a mistake lots of writers, myself included, make. It's about something completely different, it's about simplicity and precision."

Now 35 and well established as an exciting, original dramatist on the strength of that powerful trio of major plays, Carr is a formidable talent drawn to a subversive darkness which is invariably relieved by sudden comedy and some of the best dialogue yet written for the Irish stage. Exasperation is the planet most of her characters inhabit, their humour is blacker than black. A shrewd, deliberate individual, she possesses an unusual poise; she is friendly, wary, very funny and highly intelligent rather than clever. There is a naturalness about her which can be disarming. Also, she conveys a strong sense of having another, extremely normal life, well removed from solitary hours writing in a Spartan office.

Her broad, dreamy girl's face, long hair and student aura make her seem younger than she is. Her voice is low and easy, while her accent, which remains of the midlands, is further diluted by traces of the west. Her mother was from Invern, Connemara, her father is a Donegal man, and Offaly is a long county bordering Galway.

Although obviously confident of her work, Carr does not offer easy pronoucements about writing. Nor is she random or casual, giving the impression it's all due to inspiration. She is extremely disciplined, a quality she notes in others. With a second baby due in six weeks, the new play and other writing have been running neck and neck during the pregnancy.

Her work room in Temple Bar is empty and carefully devoid of distraction. A new play, Ariel, is on the desk. "I'm not quite sure what it's about," she says. There is also the manuscript of a novel and a neat group of short stories nearing completion. As a writer, she says, reading is an important part of her day. "You need time to think, to read, to do nothing and I do that five days a week."

Among the few books in the room is a lived-in copy of Heaney's Opened Ground and Richard Ford's collection of Chekhov's short stories. Chekhov is a hero, Ibsen is another - "Did you know his plays were read like novels? When a new Ibsen play came out, there'd be 13,000 copies of it sold just like that; they were bought like novels." Tennessee Williams is her muse: "He's a poet. The Glass Menagerie is my favourite play, and I love the short stories."

Within minutes of meeting Marina Carr it becomes clear that she is far more content speaking about her favourite books than she is about her own work, much less her life, which is determinedly private. From J. M. Coetzee to Annie Proulx and Nadine Gordimer, Carr's literary observations are sure-footed. "John McGahern is brilliant and I only read Eugene McCabe's Death and Nightingales about three months ago - it's wonderful," while she makes her respect for fellow Irish playwrights clear, mentioning most of them. Friel remains hugely important, and she praises Conor McPherson's The Weir.

Above all, she believes plays should be read and treated as text. "I've read far more plays than I've ever seen on stage." A former writer-in-residence at the Abbey Theatre, last year she had that post at Trinity College and is just completing a similar stint at Dublin City University. Of being a resident writer in an academic environment she says: "It's a very interesting job. I enjoyed it. I bought wine and water for my students and we sat around discussing books. Some of them loved it but others didn't, I think they wanted something more structured," she shrugs. "That did throw me a bit. But the really good students loved the relaxed environment, the glass of wine and the talk about books and sentences and paragraphs . . . but I don't think you can teach creative writing, can you?"

Her own work resides somewhere between Synge and Tom Murphy. Contrary to popular opinion there is more to Ireland than Dublin, the mythical west, the North and Kerry. Carr has created a specific universe drawing on the midlands; it is as realistic as it is surreal. No one could accuse her of romanticising her world but neither does she demolish it. This is not issue drama.

Nor are the characters trying to escape. Shalome, the genteel though demented grandmother in On Raftery's Hill is an exception: "I could be in Bavaria right now. I could've met Dracula. Instead here I am . . . " She spends the action intent on flight, but she has been trapped by many things: "All my life I've waited for my life to start and somehow it never has." As in The Mai, there is an element of class confusion. But the heart of the new play is a tragic elder-daughter-turned-mother to her siblings. Carr has consistently been able to defy the predictable. Most important of all, she has written out of the ghetto; there is no feminist message. Her plays to date feature anti-heroine female characters who are individuals and certainly outsiders, but they are neither stereotypes nor wronged Joan of Arcs.