Web of intrigue: Joanne Harris poses questions of identity in her new thriller

A thriller set in an online community? Joanne Harris has firmly left behind the French pastoral world that made her name. In its place lie intimate questions of murderous intent and skewed identity

Joanne Harris is a Cambridge graduate in Oxford, an interloper at the city's literary festival. As we sit down to coffee overlooking the quad of Christ Church College, she has a demeanour that combines a touch of Miss Jean Brodie with a dash of Cocteau Twins; the former informed by her 15 years as a French teacher, the latter referenced by a high-necked, black-leather jacket and a bass-playing habit. Harris has been a supporter of the festival for the past decade and this year has made it a family affair. Her daughter Anouchka has just interviewed Philip Pullman and, sitting serenely by our side, seems entirely unfazed by the coup, even though it appears she got some scoops.

Killer questions lie, too, at the dark heart of Harris's new novel, blueeyedboy. In it, BB, a fortysomething web-blogging loner, forms a murderous narrative through his journal at badboysrock, an online society he has set up. BB lives in the same fictional Northern town that featured in Harris's Gentlemen & Players. He spends his days considering the demise of his overbearing mother. Members of his online mob are anonymous and wicked. Or are they? Albertine, the other narrator, is a virtual, equally nebulous character. The only things that are clear are BB's matricidal fantasies. In his words, "some boy's mothers are sugar and spice. Mine was – well – she was something else."

It is, I suggest, something of a departure. "Oh, you've said the D-word," exclaims Harris, who has a long-held annoyance with instant responses to new books. However, the online communities where members are linked by common interest (dachshund breeders and Star Trek fans are the examples Harris offers), and which form this new novel's setting, are a world away from the pastoral French milieu that made her name.

I tell Harris that, being a 21st-century Luddite, I find online communities creepy. I associate the unreality with a loosening grip on morality. "Really?" asks Harris. "I wonder why. People are obviously much more scared than I am about these things. I can't see what possible risk they can present to me." She acquiesces slightly when I ask if she would have been happy had Anouchka been involved in these communities when she was younger, agreeing that a separation needs to be made by those of all ages between our real life and the one played out through wi-fi.

Her attitude that these internet hothouses are generally benign – a world where "ultimately it's only role-playing" – seems odd, considering the sinister undercurrent of blueeyedboy. It is a tale of online hoodwinking, of murderous plans dispatched into the ether. "Ah, but these are psychological problems," clarifies Harris, "that people may or may not have. The interesting thing about the internet is that it has created a kind of alternative circle of friends for people."

The nature of such friendships is carefully explored in her novel. The bloated egos and thin-skinned feelings present in chatrooms are victim to a unique form of hypersensitivity: "A little tantrum in real life seems so much bigger online." A capitalised word can be misconstrued, a smiley font becomes a mocking emoticon. It is a world of virtual bonds built on blather and jabber. "It's a completely false intimacy which is based on information you've received, essentially on trust, in most cases from somebody who is a complete stranger," says Harris. "If you are fool enough to tell these people the truth about yourself in a way that could then be turned against you, I get the feeling that you deserve everything that gets done to you."

What gets done to whom, and by whom, is the novel's recurring motif. Not that Harris has constructed a whodunnit in the traditional sense, but rather a house of mirrors in which the reader is left wondering what is fiction and what is the truth, who is behind each sobriquet and what their motivation is.

This sleight of hand is nothing new. Harris's fiction has consistently created worlds centred on "the idea of stealing a soul" or drawing up "a cloak of disguise". "I think all of my books have been in some way about this," she says. "About the questions 'Who am I?' and 'Where did I come from?' and 'Why do I do the things I do?' This is a very old idea, in so many ways. It's one of the main themes of literature, isn't it?"

Ever since movie-goers checked into Bates Motel, twisted, homicidal mother fixations, such as that found at the core of blueeyedboy, have proved familiar subject matter. "Clichés are clichés for a reason. I wasn't really thinking about Norman Bates, I was thinking about that part of us, of all of us, that has always perhaps thought about killing a relative." I can't help glancing towards her amused (I think) daughter.

While her maternal family is French, Harris was born in Yorkshire, and that cultural mélange has instilled a persistent state of otherness: neither one nor t'other as they might say in her hometown of Barnsley. "I think if you are an outsider then you are an outsider always," she says. However, she considers this state less as circumstantial than simply as a natural character trait; that there are some who are always beyond the fringes. Ironically, her position as an interloper inspires welcomes rather than wariness. "I get so many offers you can't imagine," she states. "'Please will you write a book set in our country?' It's a wonderful offer in every way, and impossible in every other way."

Harris recognises that she has several strands of readership that twine together. When Gentlemen & Players was published a few years ago, a new audience was drawn to her fiction. Suddenly, thriller fans – and men – were buying into her menacing tale of felonious public-school days. Likewise, her collection of experimental short stories, Jigs & Reels, found her trying her hand at many genres. While Chocolat created fame and the foundation for a long career, Harris has never veered from her belief in following story ideas that are anchored to her own memory and life view. Into this base recipe, she, as blueeyedboy has it, fills in "the gaps with plausible detail while the rest turns over in darkness, like a spindle laden with black sheep's wool".

A return to bucolic la vie Français is not on the horizon. "France is not a theme; it's a location," says Harris. "It's not somewhere I can decide to go on holiday in that kind of literary way. I just write the story that is there. My publishers have been very understanding in that they have given me leeway to do all sorts of things. I'm phobic about the idea of being constrained."

The shackles of expectation are a burden she has always attempted to break. "As a child at school, for a whole year, I developed a different personality for different subjects. So for one subject I would be obnoxiously talkative, in another I'd be extremely shy, and in another I'd have a certain habit. When the teachers' reports came out at the end of the year, it sounded as though they'd been teaching different children. I'm not sure quite why I did it. I was quite young, I was about 11 or 12." It sounds like a fledgling author or, as with many of Harris's characters, possibly a fantasist flitting between multiple personalities.

Some readers may be disappointed by the lack of culinary content in blueeyedboy. "There's not so much food but there is, I think, a strong sensory dimension. But it is slightly warped, because of the synaesthesia," says Harris, who has herself always associated specific colours with tastes and smells. The synaesthetes in the book are led by BB, a fictional boy in blue who represents "all flavours of unholy desire".

Of course, in a certain sector of the public consciousness, Harris will always be positioned at the intersection between gastronomy and popular literature. However, her two well-received cookery books, The French Kitchen and The French Market, have exhausted her family recipes. But what about her Northern tastes? She jokes that a former publicist took her to Betty's of Harrogate, insisting that the speciality of the famous tea shop was called a "Yorkshire Fat Bastard". In fact, their "Fat Rascal" is a plump fruity scone. So, then, no Yorkshire cookery book? "I'm not particularly au fait with Yorkshire cookery," she smiles. "I think I've eaten a Yorkshire pudding once in my entire life. It would be a very short book." An outsider to the end.

The extract

blueeyedboy

By Joanne Harris (Doubleday £18.99)

'...Bad guys make the heart beat faster – or sometimes come to a sudden stop. Which is why I created badguysrock: originally a WeJay community devoted to villains throughout the fictional universe; now a forum for bad guys to celebrate beyond the reach of the ethics police; to glory in their crimes; to strut; to wear their villainy with pride'