AMONG the items Tracy Chevalier would rescue from a house fire - alongside her husband, son and cat - is a piece of beachcombing bounty small enough to fit in the palm of her hand.

The strange, fan-shaped object looks like a flat piece of stone, but is in fact part of the shoulder bone of an ichthyosaur, unearthed by the author after days of fossil hunting on the beaches at Lyme Regis.

Part of Dorset's Jurassic Coast, this is the setting for Chevalier's latest book, based on the life of the 19th-century fossil hunter Mary Anning.

Anning herself was a bit of a find for Chevalier, 45, who came across the colourful character on a wet half-term holiday with her nine-year-old son.

"My son really likes dinosaurs, so we went to this museum in Dorchester and I saw this sketch of Mary Anning," says Chevalier.

"She was a 19th-century fossil hunter from Lyme Regis who discovered some really ancient creatures. No one knew what they were; they thought they were crocodiles. They didn't realise they were 200 million years old.

"In the sketch, she was on the beach in a top hat with a pick. She never married and was a difficult woman, and I thought: She's the one for me'."

A major part of the appeal of Anning was that very little was known about her, allowing the author a free hand in fictionalising her life. Chevalier says: "I choose subjects that there is not very much known about, then I feel confident filling in the gaps."

This was precisely the lure of the young girl in Vermeer's iconic 17th-century painting, which inspired Chevalier to write her best-seller, Girl With The Pearl Earring.

Chevalier imagined the girl to be Griet' a maid in the Vermeer household, but this was against the thinking of experts.

"A lot of art historians think she was one of Vermeer's daughters," says Chevalier. "But when the painting was done, his eldest daughter was only 12, and I think this girl is older."

Again, the book came from a Eureka' moment. Chevalier explains: "I've had a poster of that painting on my wall since I was 19 - I still have it today. Then, 15 years after having it, I suddenly went: Wow'. For the first time, I asked: What did Vermeer do to make her look at him like that?' The painting's not about her, it's about their relationship."

Chevalier reveals she was surprised by the novel's success. It has sold more than three million copies worldwide, been translated into 39 languages and been made into a film starring Colin Firth and Scarlett Johansson.

"I thought it might sell 500 copies then die a death and go out of print," she says.

"One of the great results of the book is that people write to me and say that they are looking at paintings in a different way and going to galleries."

This greatly pleases Chevalier and helps explain why she has taken up the challenge to be Writer In Residence at York Art Gallery this year.

In what is thought to be a pioneering move between a well-established author and a British art gallery, Chevalier's task includes writing a short story during her visits over the year, as well as curating an exhibition, judging a short-story competition, giving readings and allowing the public to scrutinise her work.

The part-time position is a daunting prospect, she admits.

"The more I think about it, the more I feel terrified," she says when we meet at the gallery.

American born and raised, Tracy is tall with shoulder-length, straight hair and strong features, but there is an openness about her manner.

During the photo session, she chats easily about her family Christmas in Dorset and inquires after my family. Later, she gently quizzes the gallery guides about what paintings most appeal to children. This is just as well, because while she is in York, the public will be given access all areas.

"Normally, I write in the comfort and safety of my study where I can cross out and nobody has to see the draft.

"But I don't want to be a writer in residence and not be here. It's scary and risky and maybe everything I write here I'll have to throw away, but I still think it's worthwhile to demystify the whole process."

Equally daunting, if not more so, confesses Chevalier, is the task of curating an exhibition, to be held in the Little Gallery from September.

"I'm really interested in the experience people have in an art gallery; of not liking a painting or liking a painting," she says. "I want people to feel comfortable about making judgements."

Recognised as one of the most successful novelists of her generation, and with a happy family life too, you could say she has it all. But she's not one to settle on her success - this was the woman who, after all, gave up a career in publishing at the age of 32 to embark on a writing career.

"I don't want to get in a rut. I have been worried about this. Am I always going to write historical novels and everything is going to be tickety-boo? I don't want to get complacent."

Despite the fact all her novels to date have been based in the past, Chevalier dislikes being branded a historical novelist. However, she admits to having no interest in writing contemporary fiction.

"By looking at the past I can enrichen my present. It makes me feel part of a long continuum - part of history, of people, and there's something comforting in that. When you have a kid you understand why you are here: to help the human race go on, with all its problems.

"In writing, I look back but, with my son, I'm looking forward. It makes me a more well-rounded person."

Meet the writer...

January 31: Book signing at York Art Gallery, noon-1pm

March 11: First Writer In Residence session Evening reading as part of York Literary Festival

May 7: Writer In Residence session

May 8: Launch of short story competition (closing date September 30)

July 1: Writer In Residence session

September 11: Opening of Tracy Chevalier's exhibition in the Little Gallery, York Art Gallery

November: Public reading at York Art Gallery

Prize-giving for short story competition.