'The internet is a metaphor for the human race, but also a sink in which people pour their lives'

It's an apt description for a book that is a very dark psychological thriller with a creepy middle-aged misanthrope at its centre. BB spends much of his life online, pouring out his fantasies about killing his mother on to a website called badguysrock, which caters for would-be murderers. His musings make it a difficult read at times, and even Harris herself has said she is not sure how many (if any) are dead at the end.

Presented in a series of weblog postings from BB or blueeyedboy, as he calls himself in cyberspace, the narrator deliberately blurs the lines between what is actually happening with his mother and brothers and what is pure fantasy. Supplied with each posting is a description of his mood and playlist of music he's listening to at the time. The most "real" world for BB is the one out there in the ether, and it's never completely clear how much this "reality" spills over into life outside his darkened room.

The book is more experimental than Harris's previous fiction although all of it is strange in its own particular way – from the magical realism and swiping at authority and religion of Chocolat, which became a film starring Juliette Binoche and Johnny Depp, to the prejudices and rivalries of a small French island community explored in Coastliners.

Harris, who lives near Huddersfield and was formerly a teacher at Leeds Boys' Grammar School, gave birth to the latest book after a difficult year in which she didn't write at all, and went through "rather a difficult wrangle with my agent". Finding herself exhausted by the experience, she says she spent far too much time online, hanging around on various websites and generally evading reality.

Under a pseudonym, she explored online communities, made cyber friends and began writing chain fan fiction. "I didn't set out with the errand of researching and plotting a novel about that world – I work more organically than that. Subjects tend to find me. I found myself wasting a lot of time online but then became more and more interested in the communities there and how similar they are to real life communities.

"They often have a similar social infrastructure, but responses are quicker, with people being easily manipulated and led, venting feelings, developing highly intense friendships quickly and forming gangs against each other. I found myself wanting to write a novel about that world, how people present themselves and the false basis of intimacy and trust that happens in online communities. A lot of people have become dependent on these relationships to the exclusion of real life."

Although the nature and mood of many online chat rooms can be volatile and the language used vivid or even offensive, she says she did not

feel disturbed by anything she encountered. "I felt far less

intimidated than I would if walking into a place I didn't know, among a crowd of strangers. And of course, if you don't like what people are saying or how they say it, you just remove yourself.

"There's no doubt, though, in a place where people present themselves anonymously things are said that would probably never be said

elsewhere. They feel safe to say anything. It has made me realise, more than ever, that the plainest and dullest person has secrets.

"But I think the false and anonymous intimacy of the internet is used by many people because of difficult relationships in the everyday world. I don't crave intimacy with a huge circle of friends, either real or imaginary, and unlike many of the young people who may feel alienated and dissatisfied by relationships in their life, I am cynical about what kind of replacement cyber friendships can offer."

In the actual writing, Harris says she has a clear idea of where she wants the story to go, but once a character is set in motion they can begin to reveal themselves to her in unexpected ways. "That's how I like it," she says. "If characters were too much in my control I wouldn't be happy.

"I start out with the trajectory, but not sure of how I'm going to get there and sometimes work my story into difficult spots then have to figure my way out. Luckily, I don't usually find I have to eliminate great tranches of story and experience a few 'Eureka!' moments which help to work out problems, and sometimes have to let go of something for a while and work on another part of the story."

Harris has entwined in the plot her interest in synaesthesia – a condition in which one type of stimulation evokes the sensation of another, as when the hearing of a sound produces the visualisation of a colour.

"I've always associated certain colours with tastes and smells. I'm not sure whether that makes me a synaesthete or not, but it made it easy for me to identify with the characters in the book who are. I also wanted to look at how what one person feels in the face of the same stimuli may differ completely from what another person experiences." The story also encompasses a blind character, originally the subject of an unpublished short story.

After a long intense period immersed in cyberspace, consuming the best and worst of it, Joanne Harris has come to a few conclusions.

"It's a marvellous thing – the expertise that is available either through websites of official institutions or those run by people who are obsessive about certain aspects of life. But there are different ways of seeing the internet: extremely useful, a waste of time, a great tool for bringing people together or a mechanism that cuts people off from the real world. I think it is an enormous metaphor for the human race but also a sink into which people pour their lives."

She views the linguistic shorthand and disinhibition of the web as causing changes in the world beyond the internet. "Some of those who visit chat rooms or write blogs can lack people skills and language skills. The medium also encourages bald responses, stripped of social conventions, with no particular need for politeness.

"Its wide influence means that in the real world people are getting ruder and cutting corners, with no please or thank you or eye contact. The speed at which people respond to things is quicker and they become outraged more easily. We've never had a time when the cult of the individual has been so strong, yet many of the people expressing themselves all over the internet don't seem to have that much to say. I think this phenomenon arises out of confusion and dissatisfaction with their lives."

The 140-character messaging world of Twitter comes in for a verbal exocet from the writer, who calls it "the curse of the terminally self-centred... those who are obsessed with unimportant minutiae of their lives, and think others should be interested – when the overwhelming majority of the material is only interesting to that person and a couple or small group of others at most."

The publishing world's love affair with the internet means, Harris says, that publishers "kowtow to online critics and bloggers because they have large audiences" – yet she feels some of those critics do not speak with any great authority.

The handy access offered by her own website is a double-edged sword. "It's great to be in touch with readers, it really is, but it's amazing how many people use the site to ask me to help them with A-Level essays or PhD research. I gently and politely point them towards doing the work themselves."

As the medium that produced her anti-hero BB, the man whose rich fantasy life apparently spills over into real life, Harris is healthily respectful yet sceptical of its benefits. "I love it, but at the same time didn't quite realise before how many madly obsessive people there are on the internet – harmless or not."

n blueeyedboy by Joanne Harris is published in hardback today by Doubleday, 18.99. To order from the Yorkshire Post Bookshop call 0800 0153232 or go to www.yorkshirepostbookshop.co.uk Postage costs 2.95.