It should come as no surprise that one of key characters in David Mitchell's dazzling new novel, The Bone Clocks, also featured in his last book, The Thousand Autumns Of Jacob De Zoet.

"Marinus is on his 29th life," says Mitchell matter-of-factly. "He's someone who retains memories of his former lives like we retain memories of our former addresses. A Time Lord without a Tardis or sonic screwdriver. A Buddhist version of the Wandering Jew personality."

This is classic Mitchell, and goes some way towards explaining why the 45-year-old Englishman is widely regarded as the most daring writer of his generation. While much of The Bone Clocks takes place in the realm of what might be called "real life" - there is sex, drugs, war, politics, literary feuds and Talking Heads albums - it's enveloped within a vast, cosmic framework of multiple existences, jarring time-shifts and an epic battle between two sets of reincarnated souls called the Horologists and the Anchorites. You can see why Kate Bush was so intrigued by Mitchell's imagination that she hired him to write dialogue for two scenes in her Before The Dawn show.

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The case of Marinus is not unique; numerous themes and characters recur throughout his work. I suggest he's creating a World of David Mitchell and he laughs. "You're starting to make me sound like a theme park. Eight pounds per person, or 16 quid for a family. But yes, I'm making this universe, this uber-book that all my books are a chapter of, though they all have to be stand-alone books in their own right, too. The characters must work for the book, not the other way around."

A front-runner for this year's Man Booker prize, The Bone Clocks stretches to 600 pages, with several overlapping storylines throughout its 60-year span. Mitchell acknowledges that the scope of his books "requires mutual faith and trust. The reader trusts that I won't abuse the story, and I have faith that they will stick with it". Does he always know where he's going before he sets out? "God no. Writing is an ongoing tug of love between what you plan and what you discover on the way. All my books have bits lopped off to make them work. Probably they'd all be 900 pages had I done what I daydreamed of doing at the beginning, but once you get over 600 it had better be perfect otherwise you're in big trouble."

We're meeting over breakfast in London. Mitchell is en-route to a literary festival in Denmark, having flown into town the previous day from his home in Ireland. Armed with rucksack, laptop, smartphone and a few books, he's boyish, enthusiastic and friendly. He bristles only once, and then only slightly, at the mention that the misfiring movie adaptation of his 2004 novel Cloud Atlas - starring Tom Hanks, Hugh Grant and Halle Berry - was trashed by critics. "There were a few fabulous reviews, and a few horrendous ones," he counters. "I saw how hard everyone worked, and it's rude to be snotty about that. Everyone approached it with unimpeachable integrity. It was a great honour that people that gifted would spend a good chunk of a finite number of their working years on an adaptation of a book I wrote."

Otherwise he exudes good cheer, but there's clearly a worrier beneath the equable exterior; both Cloud Atlas and The Bone Clocks end in bleakly dystopian premonitions of our future existence. "I'm an optimistic person, but not to the extent where it becomes an act of self-mutilation," he says.

"You have to be guarded, because your optimism can be used against you by the less scrupulous. It's good to have an innate faith in the better quality of human beings, but only if you're aware of what they're capable of as well." He scoops up a spoonful of yoghurt and Granola. "Steel yourself and read the papers."

Is he a political animal? "Not on a partisan level. I'm a member of Amnesty because I could have been born a Kenyan, Chinese or Romanian writer and be rotting in jail just for doing what I do, but I'm not a member of any political party."

He expresses no view on the forthcoming referendum other than the hope everyone engages with the issues and exercises their right to be heard. "You need to know this stuff. Politics is interested in you and every aspect of your life. It exposes you to danger to not know how it works, or to not vote. The blood that has been shed down the years to get you this right, and you can't be a**** to go down to the polling station?"

Mitchell personally devolved from Britain in the early 1990s. After graduating from Kent University and working briefly in Waterstones, he left in 1994 to teach English in Japan. There, he wrote his first two novels, Ghostwritten and number9dream, and met his wife Keiko, who nowadays advises him on his female characters. "She says, 'A woman just wouldn't do that'."

They left Japan for Ireland in 2002, moving to Clonakilty in West Cork, where they live with their two children. His home life, he says, involves much "juggling and frantic plate-spinning. I hold the record of shame at primary school for the dad who has forgotten to pick up the kids more often than anyone else. It's so embarrassing: 'S***, what's the time?'"

He makes a clear distinction between the author and the writer. The former is the one who gets the rave reviews and the Booker nominations. The latter, on the other hand, would rather be in his hut in the garden - "It's a bit cold in winter, I need to get the stove fixed" - dreaming up his next story.

"If I have a few days where I can't sit down to write I get very antsy, although a real validation comes from meeting readers. If 200 people have turned up on a rainy night, then the book can't be that crap. I'd rather have that than a prize or a good review."

Luckily, there's no need to choose. David Mitchell has an abundance of both.

The Bone Clocks is published by Sceptre. David Mitchell is appearing at the Assembly Roxy, Edinburgh, Thursday, 7pm.