Born in Co Clare and educated in Dublin, Denis Sampson has been living in Montreal for the past 28 years, but he doesn't really see himself as an emigrant.

"When I was growing up, everyone spoke about emigration, but what happens when you land in another country? You become an immigrant. That's the key word."

Denis was, and is, an immigrant in Canada. Brian Moore was an immigrant there, too, arriving in Toronto in 1948 before basing himself in Montreal the following year. It was this coincidence of place and of emigration/ immigration that drew the scholar from Whitegate to the novelist from Belfast: "I was intrigued by the notion of following in his footsteps."

The result is a critical biography, Brian Moore: The Chameleon Novelist, published by Doubleday in Canada and by Marino here. His previous book was a critical study of a very different Irish novelist, John McGahern, and the attraction to McGahern was very different, too: "When I was writing that book I was writing about the world I grew up in. My feeling for McGahern's work has to do with landscape and small-farm life and the river that runs through it.

"He's so rooted in his own world that he makes everything a part of it, whereas Brian Moore is the opposite - always reaching out, borrowing, experimenting with genre, dispersing himself over different worlds."

He chose to write a biography of Moore rather than a critical study because he wanted to discover how one writer can write so many different kinds of novels: "McGahern's world is one world, but literary criticism by itself can't bring together all that Moore has written."

In researching the book, he had access to Moore's papers and private correspondence in the University of Calgary and he was helped by the novelist, too - though only up to a point.

"There were letters he asked me not to quote from, letters that referred to his first wife and which he felt might upset his son. I didn't feel they were necessary to the book, so I agreed."

He disagreed, however, with Moore over the seven pulp novels that had been written for money before the publication of The Lonely Passion of Judith Hearne in 1955. The novelist wanted them forgotten - "but I had a strong conviction they were part of his development as a writer".

"He's rightly admired for his depiction of women. Women love his portrayal of female characters - they feel they communicate a truth to them - but these early, macho thrillers written for a male audience reveal another side to him, and I felt they took me to the heart of something important about him."

Movement, displacement and exile are key words, he says, in any consideration of Moore's novels, and he feels they apply to his own life, too - though he has a deep affection for Montreal where he and his wife, Gay, settled in 1970, where they have raised their three children and where they both teach - he in Vanier College ("I was taken on as the token Irishman"), she in another college.

"Not Quebec, not Canada, but Montreal is the place to which we feel very attached. It's given us an awful lot, including the opportunity to become a part of its immigrant population."

He returns frequently to Ireland - to friends in Dublin, to his mother in Whitegate, to Gay's mother in Castlecomer - and he finds it an interestingly different country to the one he left 28 years ago. It is likely, however, that he will remain in Montreal, where his eldest son is an architect, his second a history graduate and his daughter a student of the cello.

Like Moore, he's been too long an immigrant to do otherwise.

Brian Moore: The Chameleon Novelist by Denis Sampson is published by Marino, price £20