CHINA Miéville is talking about his favourite monsters. It may not be the most obvious of topics for a burly bloke in his thirties with a shaved head, an earful of chunky rings, and the title of sexiest man in politics ("It's like being the world's most buff actuary – I mean, who are the hotties in parliament?").
Nevertheless, monsters are a lifelong love for this geeky fantasy writer with a Doctor Who obsession, a PhD in Marxism and international law, and a history of socialist activism that led him to stand for Parliament in the 2001 elections.
"Tentacled monsters," he says as we settle in a bookshop on London's Charing Cross Road. "Water monsters were always my big thing – the giant octopus in It Came From Beneath The Sea, the Creature From The Black Lagoon. But I was never a one monster man, I had an open monstrous relationship. The more odd the monster, the more up my street."
Recently, Miville came across drawings he did when he was five and was "slightly amazed" that his monsters were exactly the same as the ones he sketches now. "I really have not changed at all," he says, laughing. "I invented the ninja dustbin Binjas in Un Lun Dun (his children's fantasy novel] when I was ten. A quarter of a century later I got to put them in a book."
Yet his new novel, The City & The City, doesn't contain a single monster. Nevertheless, the shadow, the ominous suggestion of one, is always lurking around the corner in this noirish, Chandler-esque crime thriller, steeped in the social and political paranoia of George Orwell's 1984. It may not be a fantasy novel in the pulp tradition of HP Lovecraft, but it contains all the elaborate world-building for which Miville has become renowned.
Why the departure? "I like the idea of trying to write a book in every genre," he says. He fancies trying his hand at a ghost story, a spy thriller, a romance, and is still deciding about pornography. "I like literary rules, protocols that you think of as enabling rather than restraints. You know the French literary movement, Oulipo, that sets all these ridiculous rules like not using the letter 'e'? I like the idea of genres as a kind of pulp fiction Oulipo." He had been mapping out the intersecting cities of the book, Beszel and Ul Qoma, for many years and decided to locate his detective there, Inspector Borl, and, of course, a crime; the murder of a young woman that leads Borl to cross the border from Beszel to Ul Qoma.
There was another reason for turning to crime. Miville's mother, a liberal one-time hippie who called her son China because it's cockney rhyming slang for "mate", became terminally ill. She was a huge crime fan, and though Miville was working on another of his baroque fantasies, he decided to write a novel for her at the same time.
He got two thirds of the way through before his mother died. "I didn't finish it in time," he says. "It was done for her and she would have loved it. But anyone who goes through a bereavement is anxious about becoming a grief bore. I don't mind talking about it but there is a danger of sounding mawkish and I don't want to seem, I don't know… the book has to stand on its own."
It is Mieville's piecemeal formation of Beszel and Ul Qoma, cities at once familiar and strange, located somewhere on the edge of Eastern Europe, that makes The City & The City so compelling. This is where his taste for the fantastic comes in, particularly with the foreboding idea of Breach: what happens when you cross from one city to the other. There are some very satisfying twists in this labyrinthine tale. "I'm really interested in cheating," he says. "In the case of Beszel and Ul Qoma the set-up is basically ridiculous and people cheat because they have to, but at the same time, if you acknowledge cheating then the structure collapses. There has to be some power in place, and I like being vague about what that power might be. Is it devils? The supernatural? The government?" Or, I venture, is it monsters. Miville grins: "Quite."
• China Miville will be appearing at the Edinburgh International Book Festival on 29 and 30 August. The City & The City, Macmillan, 17.99 www.chinamieville.co.uk