Every novelist has a different relationship with his or her characters. David Mitchell's write him letters. "It's true," he says, rummaging for a notebook and flashing a double spread of intricate handwriting. "At the top here," he says, "we have things like 'Dear Dave', if they know me very well, and 'Dear David' if they're being more formal. Then they write about who they are, childhood experiences, first memories, what they think about other people in the narrative, what they think about God, money, work, sex, Conservative-Liberal politics, which newspaper they read. Their education, of course. The point about it being a letter rather than a biography is you're getting it in their own voice. You're in search of a voice." He thinks for a moment. "What they're afraid of is important. And what they want."
Both his breakout third novel Cloud Atlas (2004) and last year's The Bone Clocks were giant zones of experiment, splicing interlinked fictions into symphonic fantasies that contained multitudes and spanned centuries in time and literary genre.
The grand ambitions of Cloud Atlas attracted the grandiose ambitions of the Wachowskis, directors of The Matrix, who adapted it to film in 2012. Mitchell, who says it was a "very positive visit to the republic of film", has recently sold the rights to adapt The Bone Clocks as a television mini-series. In between those two landmarks, though, he also wrote a semi-autobiographical novel set in 1970s' Worcestershire and one set in 18th-century Japan - and now, in this year's short novel, Slade House, he's written a ghost story, or at least, as he puts it, "a compendium of ghost story outcomes".
It's a startling body of work to have emanated from one mind. I meet Mitchell, who is tall, lean, boyish, squeezed into a table in a hotel cafe in Cork, where he has lived since 2002 after stints in Italy, Japan and Britain. He has an air of such quiet rationality that one almost wants to question his credentials. You might peg him as the friendly sidekick, dispatched to give interviews while the real Mitchell sits raving about immortality and apocalypse.