She's Britain's biggest selling female author and yet her subjects are unsavoury - her latest novel describes a high school shooting. So what makes Jodi Picoult a runaway success? Women's Editor Sarah Foster looks into her world.

THERE is a sense with Jodi Picoult that she has life all figured out. We meet at lunchtime in a restaurant and she is relishing her food - a healthy portion of risotto. When this is done, she orders cheesecake and makes short work of this as well. It is a pleasure to watch her eat: she's unselfconscious and talks and laughs between each bite. She seems a woman who is happy in her skin.

And well she might be. At 40 years old, she's reached the summit of her craft. Although American (she lives in Hanover, New Hampshire) she's just as popular in Britain, where every book that bears her name appears to fly off bookshop shelves. Her central subject is the family, though she explores a range of issues that most would rather not encounter, and though she is a hot-shot writer, she's still a good old-fashioned mom.

"That's definitely the most important," says Picoult (pronounced Pee-ko) of raising three exuberant children. "I spend about three months of the year on the road and it is hard but it's a necessary evil, and it's easier now - my husband is fantastic with them. I talk to them almost every day and we email. I try to be there for the really important stuff - plays, graduations, concerts, recitals."

If she appears to have it all: the great career, the perfect family, then you believe she really does. She's full of energy and verve, her corkscrew curls a reddish mass, and when she smiles with perfect teeth, she shines with warmth. Yet you'd be wrong to think that Picoult was laid back. In fact, behind her apple pie charm there lies a passion to succeed.

She may be well established now but she fought for years to make her name. "I look like a fast success in Britain but it's been a very slow 15-year growth in America while I found readers who wanted to read that kind of book," she says. "Apparently, I'm now my own genre, which is good because, hopefully, the next writer who wants to write about moral or controversial issues will find it easier to get published."

Picoult relishes the difficult issues she takes as her subjects. From a child suffering from leukaemia who has a sister born to save her (My Sister's Keeper), to those who perish in Nineteen, her book inspired by high school shootings, she turns the family on its head and looks at heartbreak and disaster. But is she simply being macabre or does she have a higher purpose? She claims her writing is a means of seeking answers.

"I don't know the answers to the questions and that's what makes my books more interesting for me to write," says Picoult. "I think I'd go crazy writing a safe, happy little book every time. For me, part of the process of writing a book is to be able to wander through those moral grey areas in situations that are rarely black and white."

She wrote her first novel - Songs of the Humpback Whale - with her first baby on the way, and she admits that being a mother has helped to shape her as an author. What give her constant inspiration are her anxieties and fears. "Most of the stuff I tend to write about comes from the fears that I have as a mom," says Picoult. "The range of work I've done recently has been from 'what if your child was suicidal?' to 'what if they were sexually abused?' to 'what if they were really sick or in a school shooting?'. If I'm worried about these things then it makes perfect sense that the rest of the world is too."

Of course, by being controversial, she runs the risk that life will clash, as recently happened just after Nineteen went to print. If the gunman's rampage at Virginia Tech made Picoult feel a little awkward she's keen to act as if it didn't. "My book came out in March in America so it was out a while before Virginia Tech," she says. "That's a different case - it's a college shooting, and college shootings are different from high school shootings. Most high school shootings are firmly based on a long term reaction to bullying and intolerances."

Having studied real-life incidents - including the Columbine tragedy - she knows the subject pretty well. She says that good research is vital and is forensic in her scope. "Certainly in this case I did a lot of research with the police who were responsible on the day of Columbine," says Picoult. "I was given tapes of the shooters that were not released to the public and I was put in touch with grief counsellors who were responsible for telling the families. They were told by the police to tell the families 'your child was the first to die', and this was done out of kindness, but when they started talking and realised not all of their children could have been first it really compounded the tragedy."

In Picoult's fictional account, the child responsible for the shootings, the oddball loner Peter Houghton, had suffered bullying all his life. His actions seem, if not quite justified, then understandable. Does Picoult see him as a victim? "I have sympathy for what led him to that moment. I don't find him a sympathetic character, however," she says. "I lost him the moment he said 'how many did I get?'. The moment the victim picks up the gun he becomes the biggest bully of all."

She can appear the moral crusader - "why have we learned nothing? Why, in a post-Columbine environment, do we have anti-bullying policies and no idea of how to put them into practice?" But she is also just a mother who sees the world as being fractured. She says her writing can be painful, that there are things she won't explore.

"It's sometimes very, very hard," admits Picoult. "Nineteen was hard, doing research with paediatric cancer specialists was the same. You go home and want to hug your kids until their little heads pop off. People always say is there something I couldn't write and it would be something I was living through at the moment."

The key example Picoult gives is when her son was very ill. He had a tumour in his ear which meant substantial hearing loss and for four years, the situation was "traumatic". Yet while avoiding it at first, she did adapt it for her writing. "It affected the family very deeply and yet the lessons that I wanted to take away from that wound up becoming part of My Sister's Keeper," she says.

Now that she is a huge success, she aims to keep on writing books - she isn't precious in the least and says her secret is hard work. As long as readers keep on buying them, she hopes to give them what they want. "I feel like I've got more stories to tell so, hopefully, there will be plenty more people out there to read them," says Picoult.

Nineteen by Jodi Picoult (Hodder & Stoughton, £14.99)