The words "Jodi Picoult" and "controversy" are, at first sight, as unlikely bedfellows as "Frankie Boyle" and "subtlety".

After all, what could be controversial about a married mother of three who grew up in the suburbs of Long Island to become a bestselling author?

Those few individuals who haven't read a Picoult novel are about to find out, as her latest book is possibly her most newsworthy yet. The begetter of the "what would you do if..." kind of novel, over the course of the last 20 years and more than 20 books, she has involved her readers in numerous ethical and moral dilemmas, selling several million copies in the process. What would you do if your sister needed a bone marrow transplant and you were the only match for her (My Sister's Keeper)? What if your son had Asperger's and was suspected of a crime (House Rules)? What if you wanted to have a child using embryos fertilised by an ex (Sing You Home)?

This time, in The Storyteller, Picoult has focused on the Holocaust. She asks, what would you do if a former Nazi concentration camp guard begged you to kill him and asked you for forgiveness?

I'm intrigued to know just how hard it was for Picoult to write this novel, but it wasn't over-eagerness that had me calling her at her New Hampshire home at 4.45am, just an unfortunate mix-up over times. I woke her up, needless to say, but she "was going to get up in about half an hour anyway for a walk," she tells me. For those looking for the key to bestseller success, there's a clue: get up at 5.15am, go for a walk, then get writing.

Despite the rude awakening, Picoult doesn't sound in the least fatigued and insists on doing the interview then and there. "It was definitely a daunting task," she says about the novel, straightaway. "But I wouldn't have not written it because of that. I knew basic student facts about the Holocaust, but I hadn't studied it, it was never a passion of mine, so I needed to acquaint myself with the facts." And once she'd done so? "It definitely felt like an achievement to get through it. Because even though I'm writing fiction, I feel like I've been trusted with the survivors' stories, and that's important."

What was the most difficult part, other than the research? "It was harder to write from the Nazi point of view – you don't see a lot of that, and it was hard for me to imagine an ordinary German point of view." There were acts of kindness shown to survivors by German soldiers, she says, and she felt it was important to include that, too, to show as full a range of behaviour as possible.

Picoult also says that she sees herself as an outsider, which is possibly where her empathy for those caught in ethical dilemmas comes from. She was born on Long Island and educated at Princeton, where she did a course in creative writing and has acknowledged the help of her tutor, the writer Mary Morris, in her career. After Princeton, she completed a Masters in Education at Harvard.

There can't be too much about her life that makes her feel like an outsider, but she wrote very eloquently two years ago about her son's homosexuality and acceptance, especially in middle America ("What does it mean to be gay today? How do we define a family?" she asked). With her latest novel she acknowledges her own Jewish heritage, as her mother was Jewish, but she also defies it. "I'm not a religious person and I don't consider myself Jewish," she says. "I write about groups I'm not a part of. I can still write that story. Sometimes people take more notice when an outsider is the one talking anyway. An insider is just thought of as complaining."

Her new novel was inspired by renowned Nazi-hunter Simon Wiesenthal's memoir, The Sunflower: On The Possibilities And Limits Of Forgiveness, and she quotes from it at the beginning of her novel. "He writes about being in a concentration camp and being called to the bedside of a dying Nazi soldier who asks him to help him atone for what he has done to the Jews," she says. "It's startling but he doesn't forgive him, he didn't think it was right to forgive him, and his stance has been analysed by thinkers and philosophers ever since. It made me wonder, what if that were to happen today?"

In The Storyteller, Sage Singer is a young woman who has been disfigured in an accident. That's why she works in a bakery at night-time, so she won't have to meet people. But one customer confronts her. An elderly resident of the town, Josef Weber is a friendly old man who is highly regarded by his local community for all the work he has done over the years. Weber has a past, though: he was once a guard in a concentration camp, and now he wants Sage to kill him, to atone for what he did back then. Sage's Jewish grandmother, Minka, survived internment in just such a concentration camp but her sister didn't. What kept Minka alive, as we discover from her historical narrative, was her ability to tell stories – like Scheherazade, she would spin out tales for a camp commandant who enjoyed them enough not to let her die with everyone else.

Does Picoult believe that stories really can save people's lives? "I think they save people all the time," she says without hesitation. "They save writers' lives and they certainly save the lives of the readers. I have thousands of readers who tell me 'I was suicidal', or 'I was date-raped', things like that, kids who feel marginalised and who say, 'you made me feel normal'."

Her novel tackles probably the largest subject she can think of – the nature of good and evil. In a separate narrative, the young Minka writes a fantasy tale about vampires, taking a Polish legend about blood rites and how drinking the blood of the vampire will protect you. But even that has an ethical aspect. "What makes a monster a monster? Can you have a conscience and still be a monster? I think the line between good and evil is constantly shifting; you can do something bad for a good reason, for instance. But I do think if you do something awful it will stay with you forever."

Picoult is known just as much for her focus on the family as she is for her love of difficult issues, and in The Storyteller the two aspects combine with great power and force. "More than being about mothers and daughters, this book for me is about family and how important family is. The great casualty of the Holocaust is how the family is disintegrated. That's almost more important than Sage discovering her own historical past. It's about the ties that bind us."

What is fascinating about Picoult is that people aren't discouraged by her focus on morally tricky issues. On the contrary, they love reading about them, thinking about them, debating them. If ever there was a perfect "book group" choice, ripe for juicy discussion, then it has to be a Jodi Picoult novel. Yet this very discussable quality in her work, together with a suspicion of "formula" over-employed, has been controversial in itself, with one commentator even asking if Picoult's novels are "bad for literature". Picoult herself sparked off a huge row two years ago about how often books by women writers get reviewed, when she complained that novelist Jonathan Franzen had received two glowing reviews in the New York Times. "Is anyone shocked?" she tweeted. "Would love to see the NYT rave about authors who aren't white male literary darlings."

If Picoult is writing about family issues that are just as important as the ones Franzen fictionalises, then why is she, like many women writers, ignored by the literary establishment? The answer seems to be anti-commercial feeling (although plenty of commercial writers are covered by broadsheets, both male and female). There's something about Picoult, I suspect, that makes some people indignant and a little bit sniffy. As though they think she shouldn't be dealing with heavy ethical or moral dilemmas in what is essentially a popular package. As though she's too light for the serious stuff. If that really is the case, then The Storyteller should truly upset them. One suspects, though, that Picoult will quite enjoy that.

The Storyteller, Hodder & Stoughton, £18.99. Jodi Picoult will be speaking at an exclusive Herald literary evening at 7pm on Tuesday, April 2, at the Mitchell Theatre, Glasgow. You will have the opportunity to meet Jodi and have your copy of her book signed. Tickets £13; box office 0141 353 8000. For details go to www.glasgow concerthalls.com/whatson