Cloud Atlas writer David Mitchell says he believes he has created his own version of Middle-earth for all his future books.

Teasing a book festival crowd recently with excerpts from his forthcoming novel, Slade House, he says it would inhabit the same Newtonian law-bending universe of 2014’s The Bone Clocks. It is “by far the darkest book I’ve done”, he says, and “an exercise in world-building and cosmology”.

Mitchell again plans to jump from genre to genre within the book.

“I like to use genre as a tool, like style, structure or a character. Where does it say a book has to remain within a single genre? Why can’t more than one genre occupy the space between the front and back cover?”

He adds that “fantasy is the easiest genre to do badly. Perhaps it’s the hardest genre to do well.”

But there’s one road he’s reluctant to go down: writing as a woman. Asked about his experience of writing in the female voice, he says: “It is scary. You get more cautious as you get older. I probably wouldn’t write as an American either. I’d find a reason to make them half British.

“I’m aware that female writers have been writing brilliant female characters for hundreds of years. I could make a terrible fool of myself unless I work out what the traps are, find bad female characters by male writers, work out why they’re bad and give my wife every single manuscript to read.”

The realisation that he was creating his own universe along the lines of J.R.R. Tolkien’s in The Lord Of The Rings came in a conversation with his editor, says the author, who has been longlisted five times for the Man Booker prize and shortlisted twice.

“You’re making your own Middle-earth aren’t you?”said his editor, to which Mitchell replied “Yeah, I suppose I am. I love large-scale exercises. The size of that world, that is the theme.”

He adds: “Everything I will do will be in this universe. Even if it’s the book after the next one I do, which will be set around the turn of the first millennium.”

Slade House first saw light of day as a Twitter novel, The Right Sort, last year. But Mitchell says the story “asked more questions than it answered”, so, he “re-translated it out of Twitterese and into English”.

Translations have been a big part of Mitchell’s career. He previously taught English in Japan. Asked about the adaptation of 2004’s Cloud Atlas into a Hollywood movie, he says plot changes were “absolutely necessary”.

“I trusted the directors and I think I was right. They never betrayed the trust I placed in them. I was never really worried, more curious. – Guardian News & Media