As a rule, Anthony Horowitz doesn't wear shoes with laces.

But if he does, he usually ties his right lace first. That is why, if his latest book is to be believed, he'd make a lousy assassin. Tying the same lace first is a pattern, a tell, you see. And patterns, tells, give you away when it's your job to kill people.

Of course, as he also points out, it's not Anthony Horowitz's job to kill people. But it is his job to write about people who do. People like Yassen Gregorovich, the "hero" of Horowitz's latest novel Russian Roulette, the latest in his hugely successful Alex Rider series (a staggering 13 million English language sales). It's a prequel, actually, telling the back story of the Russian assassin, a recurring villain in the series.

The result is a bone-hard, fast-paced and nastily inventive novel - two parts James Bond thrills to three parts Jason Bourne chills. There's the destruction of an entire town, the murder of Gregorovich's parents, slavery, torture and various murders carried out in interesting ways. Surprisingly dark, then, for a book for young adults.

"I don't think there is anything that young kids - ten-year-olds - won't be able to handle," Horowitz tells me when I suggest as much. "If you look at my last book, Oblivion, it's full of violence and death. It was a very dark book. This one is much lighter than that."

Anyway, he says, "the Alex Rider series was always conceived as adult books for children. I think part of the success of the series was that it was fairly unrelenting. It didn't pull its punches and, as the books continued, they got darker as they went along because I was always aware my audience was growing up."

Horowitz is sitting at a desk in a friend's villa on Crete as he tells me this. "I've a very beautiful Aegean in front of me, which is a dazzling blue. A totally cloudless sky. There is a sailing boat tickling past but nothing much else at the moment. A couple of olive trees on the hill. It's very, very peaceful."

He's on holiday. Except, it seems, he doesn't really do holidays. There's a computer in front of him and he's working on his TV series, Foyle's War. There are also 36,000 words of his new Sherlock Holmes novel, a sequel to his first take on Conan Doyle's world, House Of Silk (he can't tell me what it's called yet but he will say it takes place after Holmes and Moriarty have taken a tumble off the Reichenbach Falls and concerns itself with "Moriarity's last crime"). He will do another two hours of work tonight before dinner.

Writing is another tell when it comes to Horowitz. Perhaps the key one, really. If you trace the pattern it makes in his life you have the outline of the man.

To help make that pattern out I've stolen some questions asked of Gregorovich in Russian Roulette to try out on his creator. For example, what was the best present anyone ever gave you, Anthony? "My immediate answer is a human skull that sits on my desk. My mother gave me that for my 13th birthday. My wife Jill for my 50th birthday bought me the most amazing toy. It's an animatronic day in a writer's life. You push the button and it shows you what happens to a writer from morning to night."

What is his favourite food? "That one's easier. Chocolate digestives and tea." Anthony, tell me about your grandfather? "I have very little memory of him. I've written a book about my grandmother, who was a vile and horrible woman. And the one thing I can remember was being moderately relieved when my grandfather died because he didn't have to live with my grandmother any more."

Horowitz's family story is rehearsed in every interview he gives, but that's hardly surprising. It has a storied richness to it. He lived in Stanmore in north London, an unhappy Jewish boy in a huge house with servants. A gong summoned him to dinner. There wasn't much affection at home. And there was misery at school, where he did not succeed academically. His father was a millionaire lawyer whose fortune seemed to dissolve away when he died of a heart attack. Horowitz was 22 at the time.

The question I want to ask is whether that childhood - which from a safe distance seems rich with novelistic detail - informed his own desire to tell stories. "No," he says politely but emphatically. "It's the opposite, in a funny way. I can tell you clearly that I was writing stories when I was very young. From the age of eight onwards. My father ridiculed that. It was one of the strange and unhappy facts that I remember very clearly. He ridiculed my desire to be a writer.

"For me, writing from the very earliest days was an escape, both from the school I was at but also from my family and from that sense of inadequacy as a child. I think you'll find that in a lot of writers, especially for young people. The sense of a failed childhood. A childhood that for some reason - I never call it an 'unhappy' childhood because it was so privileged and so wealthy, how dare I use such a word about it - but none the less it was not a particularly successful childhood and I think to some extent the books were compensations. And certainly when I was writing them I remember I was writing myself out of where I was.

"If you live in Stanmore, the world's most boring suburb, and you are trapped in a wealthy, frankly dysfunctional family, then you look for trapdoors. You look for escapes. I used to look for secret passages."

In the end he found one. He did manage to write himself out of where he was. He dropped out of a career in advertising to become a successful TV screenwriter, but it was his idea at the turn of the century that it was time to reinvent James Bond that truly rewrote his life. The teenage spy Alex Rider was the result. A boy's dream life, you might say.

Or in Yassen Gregorovich's case, a boy's nightmare. Russian Roulette is set in Russia at the turn of the century, a world already gone, Horowitz suggests, buried under consumerism and the rise of the oligarchs. "I don't want to generalise about an entire country but I think what has happened to modern Russia is a catastrophe and a tragedy of the worst order. I think it is a country that has been horribly short-changed by very dubious people and I think that it's tragic that communism should have given way to something almost worse."

He spent a week in Moscow for research, to try to find where a provincial boy would have washed up in the city. "I was able to walk around little bits of Moscow that had been preserved since the year 2000. You get a sense of the graffiti and the ruin, the emptiness of it and the squalor. It was nice to go to the station and try to, as I often do when I'm doing my books, walk out with the hero's eyes. To imagine you're a 14-year-old boy. I can't pretend I did extensive research but I did at least smell the air."

And then, the trick is to reduce that research into a few words or sentences. "Kids are not interested in the economic and political situation in Moscow in 2000. What they want to know is who's going to get shot. But at the same time it's important it feels authentic. That's what I was trying to go for. If you look at the Alex Rider books, they are all the same. They are all researched but that is only the canvas. The story and the pace and action and the violence and the chases are what matters."

His own teenage sons, Nicholas and Cassian, are his first readers and his first critics. Cass was the first to read Russian Roulette. "And as usual his criticism was merciless. Total rewrite after his comments."

They are a close family, he says. That's the pattern of his own family life. Has he been keen to construct a domestic story very different to the one he grew up in? "I think I've gone out of my way to make sure my children will never talk about me the way I talk about my family."

Anthony Horowitz has tied up the loose ends of life. There are worse patterns.

Russian Roulette by Anthony Horowitz is published on Thursday by Walker Books, priced £14.99