Such a deceptively sweet title for such a dark, troubled, troubling book. Joanne Harris’s latest novel is set claustrophobically in a small house in a small town in Yorkshire, but much of the ‘action’ takes place online, told through posts on an Internet site.

Or does it? Harris’s storyteller has become a master of virtual reality. He’s in his forties, the last surviving son of three brothers, living alone with his mother, and dreaming of killing her. He’s in a dead-end job, and lives out his life through the web journal on his website badsguysrock. And it really is a ‘bad guys’ website, full of murderous fantasies.

Not a nice character in the slightest, is Blueeyedboy. Nor is his mother: she named her three sons Black, Brown and Blue, and dressed them in their respective colour at all times, to simplify the sorting out of washing. Colour plays a huge role in this book, influencing the characters of the three brothers. Blue himself has synaesthesia, seeing things in terms of colours. So, too, has the little blind girl next door, who ‘sees’ colours in music. Or do they?

Blue hates his mother, but he loves this virtual life and his correspondence, through the website, with his ‘friends’. And, because it’s a website, and because Blue doesn’t want us to know, we don’t know what’s true and what’s fantasy.

The story doesn’t exactly unfold through the website — it unravels and then ties itself up in knots. We learn more about the deaths of his brothers, but then Blue’s identity itself is not what it seems — although nothing is what it seems.

Blueeyedboy is unquestionably a masterpiece of deception and fantasy, in which Joanne Harris makes the very most of the scope for the blurred area between fact and fiction, the revealed and the unrevealed in the virtual world. Clever, of course, but this doesn’t mean it’s a pleasure to read. Troubling subject matter; unsettling; it’s altogether a very contemporary story with a chilling theme about dysfunctional families and online living.

Joanne Harris will launch Blueeyedboy at the Oxford Literary Festival on Sunday. She is also appearing at events today and tomorrow. See www.oxfordliteraryfestival. com, box office 0870 343 1001.