Mary Lawson is related to one of Canada's most adored writers - LM Montgomery, author of the classic Anne Of Green Gables series, about the early 20th Century adventures of a flame-haired orphan.

"It is not an advantage if you want to be a writer to be related, however distantly, to an icon," says Lawson, who is no literary slouch herself.

Her third novel, Road Ends, centred on a large, dysfunctional family's troubles in the wake of a tragic death, is about to be published. Meanwhile, her two previous books, Crow Lake and The Other Side Of The Bridge, are coming out in new paperback editions - a trilogy that celebrates Lawson's powers as a gifted storyteller, whose writing style is elegant and spare, with never a word wasted nor a redundant cliche employed nor an iota of sentimentality allowed.

Nonetheless, she did grow up in the long shadow cast by Lucy Maud Montgomery, who sold more than 50 million books worldwide, and whose family roots were Scottish. The connection is distant - Montgomery was a cousin of Lawson's grandfather - but it has always been a matter of family pride. "Yes, she was rather rammed down our throats, but quite justifiably. She is a very great writer. However, I would rather just make it on my own merits. But there she is, she is unreachable. I could never in a million years get to be such a literary icon," says Lawson.

Well, she is not doing too badly, however much the lady doth protest. Now 68, she looks decades younger, with her immaculate grooming and ash-blonde bobbed hair - Canadian-born Lawson is "a literary latecomer" like Carol Shields and Penelope Fitzgerald and Mary Wesley. She was 55 when her first book, Crow Lake, was published. The story of how this remarkable bestseller, which has been compared to many of the great 19th Century novels of provincial life, came into being is a saga in itself.

A graduate of McGill University, Montreal, Lawson was 22 when she arrived in London on a six-month holiday. She never went home to southern Ontario, where her father was a research chemist and her mother a teacher, because she found a job as an industrial psychologist.

At work she met and fell in love with English psychologist Richard Lawson. They married and now live in Kingston-upon-Thames. They have two sons, Nick, 38, and Nathaniel, 36, and two grandchildren. The whole family returns to Canada every year, holidaying in a beautiful summer house on a lake in northern Ontario. "It's on its sixth generation," she says, despite the fact you can reach it only by water. However, the Lawsons are keen canoeists even on the Thames, though obviously not during recent deluges.

When her boys were small, Lawson was a stay-at-home mum, writing short stories mainly for women's magazines. She was moderately successful. "They were formulaic stories because that is what the magazines wanted - boy-meets-girl romances. It was not what I wanted to write, but it was certainly a terrific apprenticeship," she says when we meet in her publisher's London offices across a small boardroom table - a much too formal a setting for this least formal of writers.

One day she submitted a story set in Canada to the now-defunct Woman's Realm. "The editor called and said it was not the magazine's sort of story - which I knew, of course - but she also said she was going to publish it anyway. 'You've got a novel here,' she told me. 'You have to set it in Canada. When you write about Canada, your writing moves up a notch.' I lost touch with her because it was many, many years before Crow Lake finally got published. I owe her a lot, however, because getting your work published is all about luck."

Lawson knows a lot about luck - both good and bad. For four years Crow Lake amassed piles of rejection slips, although she wrote the book for herself first and foremost, never expecting it to get published. "But it was painful to be constantly turned down," she says. She was half way through her second novel, The Other Side Of The Bridge, when offers came in from three agents wanting to represent her. A fierce bidding war ensued; Crow Lake was translated into 23 languages and published in 25 countries. It became a New York Times bestseller, toppling Ian McEwan's Atonement from No 1 on the Canadian lists where it remained for 75 weeks.

The Other Side Of The Bridge was published in 2006; it made the final 13 for the Man Booker Prize and was selected for the Richard & Judy Book Club. It also became an international bestseller.

"I had had no idea I would write two books, let alone three," Lawson says. "I had a two-book deal after Crow Lake, but I never thought I would write a third novel. I find getting the idea for a book very hard. It has taken me almost seven years to write Road Ends. Ideas just do not come easily to me. And then when they do, I rewrite constantly, revising line by line."

Ideas aside, she has a compelling sense of place - the remote, invented town of Struan, on the unforgiving northern edge of the wilderness of lakes, rocks and forests that forms the Canadian Shield. All three novels are set in this area, with its sawmill, local mine and farmlands, where families scrabble a bleak living in extreme weather. Struan is "a sorry bunch of stores lined up along a dusty main street," boasting only the Hudson Bay Company, post office, bank, restaurant, bar and hotel.

"I so loved writing Crow Lake that I set the other two novels in the same area," says Lawson, whose two brothers help with geographical details, while her psychotherapist sister is one of her first readers. Lawson's husband, now retired, travels with her and also helps with research.

"I really hate doing research and because I grew up in a remote farming community - actually some 400 miles south of the fictional Struan - I did not have to do any fact-checking. I grew up in just such a town, where there was nothing to do but read, for which I am immensely grateful. I called my fictional town Struan after I looked on the map to see if there were any Scottish towns that did not have a Canadian counterpart. There are not many because there are so many Scottish communities. Eventually, I came up with Struan (a small village on the west coast of the island of Skye, also a rural community in Perthshire) although I have never been there. I guess I ought to visit."

A heartbreakingly good read, Road Ends is told through the different perspectives of three members of the Cartwright family - father Edward, daughter Megan and eldest son Tom - shifting back and forth in time between Struan, Swinging Sixties' London and the silver rush in northern Ontario in the early 1900s.

The novel was heavily inspired by the Norwegian Expressionist artist Edvard Munch's painting The Scream. "I was two years without an idea in my head after The Other Side Of The Bridge," says Lawson. "Then I went to Norway on a book tour. I had a free afternoon in Oslo so I went to the Art Gallery, where there is a room devoted to The Scream - Munch did several versions. There was a plaque beside one saying, 'His companions at the far side of the bridge appear to be unaware of his anguish.' I had never noticed them before. When I looked, I saw they seemed to be just chatting and there is this guy at the end of his tether. What if he jumped? What would they do?"

But there was another catalyst, too. "Some years ago I saw an unforgettable TV documentary in which a family allowed cameras to record how a mother and father interacted with their son, who was out of control. The shattering moment for me came when the father, who repeatedly lost it with the child, was asked about his relationship with his own father. The psychiatrist asked him to describe it in three words. He said, 'Fear, anger, fury.' Afterwards, the psychiatrist turned to the camera and said, 'We learn our parenting from our parents.' I know I have made a lot of the mistakes that my parents made, for instance. Family dynamics fascinate me, as does the notion of nature/nurture. So I guess Road Ends is strong stuff."

Unable to imagine not writing, Lawson hopes it will not be another half dozen years before her next book is in print. "I get very antsy when not writing," she says. She does not know whether her fourth book will be set in Struan. "I am in love with that landscape," she says. "When I am not writing about Struan, I really miss it although it does not exist - well, only in my head." And, happily, in her many readers' minds, too.

Road Ends by Mary Lawson is published by Chatto & Windus at £16.99; Crow Lake and The Other Side Of The Bridge are published by Vintage at £7.99 each.