Alan Moore can't be accused of playing it safe. In his 40-year career, he has written a genre-busting superhero comic (Watchmen); a graphic novel in which the hero is a terrorist (V for Vendetta); and one of the most beautiful -- but scandalous -- pieces of pornography ever produced (Lost Girls).

Since 2008, he has been occupied largely with writing his second novel, Jerusalem, due for publication next year. It could easily be the oddest novel ever written. Ostensibly a history of Moore's home town, Northampton, it features his favoured technique of appropriating characters from other literary works; the author describes its middle section as being like a "savage, hallucinating Enid Blyton".

Its wider purpose, Moore says, is to "disprove the existence of death" -- but that is if he can get it into print at all: it will clock in at 750,000 words, making it longer (by far) than Vikram Seth's hefty A Suitable Boy and David Foster Wallace's Infinite Jest. The book is so long that the only printers who might be able to tackle it are Bible-makers.

“It is a very big book -- but it's very readable," he assures me when I call to ask how it's going. "Apart from the Lucia Joyce chapter, which is completely incomprehensible." How so? "It's all written in a completely invented sub-Joycean text. I read it through again and I can actually understand most of it -- well, all of it. But it's the only way I could have written that stuff. It's an experiment."

Then there's chapter 29, composed in the form of a stage play by Samuel Beckett, based around one of the times the playwright visited Northampton to take part in a cricket match. (I'm not making this up: the 1925 and 1926 matches appear in Wisden, which records that Beckett was "a useful, left-arm, medium-pace bowler".) While his team-mates took off in the evenings to patronise the city's pubs and prostitutes, Beckett decided instead to go on a "church crawl". It is this event that Moore is restaging.

Apart from these literary jeux d'esprit, the main thrust of the book explores Moore's belief that time doesn't work the way we think it does. "I've come to think that the universe is a four-dimensional site in which nothing is changing and nothing is moving. The only thing that is moving along the time axis is our consciousness. The past is still there, the future has always been here. Every moment that has existed or will ever exist is all part of this giant hyper-moment of space-time."

Confused? Moore puts it this way. "If you think about a standard journey in three dimensions -- say, being in a car driving along a road, the houses you're passing are vanishing behind you, but you don't doubt that if you could reverse the car, the houses would still be there. Our consciousness is only moving one way through time but I believe physics tells us all those moments are still there -- and when we get to the end of our lives, there's nowhere for our consciousness to go, except back to the beginning. We have our lives over and over again."

Moore is friends with (and revered by) several leading physicists -- many of whom will gladly tell you there are probably more than three spatial dimensions. He is particularly taken with the pop-star-turned-TV-populariser of science Brian Cox, and asked him recently: "How do you square the second law of thermodynamics with your earlier assertion that 'Things Can Only Get Better?'" (This joke is very funny to only a very small number of people.)

Surely Moore must be worried that, in the age of Twitter and rolling news, no one will ever finish his super-sized masterpiece? "As long as I finish it," he says. "Although I have doubted that people will even be able to pick it up. I'm not averse to some kind of ebook, eventually -- as long as I get my huge, cripplingly heavy book to put on my shelf and gloat over, I'll be happy."

That said, he does worry that while his first prose novel, Voice of the Fire (published in the mid-1990s), took 300 pages to cover the county of Northamptonshire, Jerusalem uses 750,000 words to explore an area of Northampton about half a square mile across. "So the next one will be several million words and it'll just be about this end of the living room."

Moore says he hopes never to write anything as long as Jerusalem again but he won't countenance scaling it back. "Any editor worth their salt would tell me to cut two-thirds of this book but that's not going to happen. I doubt that Herman Melville had an editor -- if he had, that editor would have told him to get rid of all that boring stuff about whaling: 'Cut to the chase, Herman.'"

One question remains: how do you celebrate finishing a 750,000-word novel? Moore pauses. "I'll probably have a bit of a lie down."

The full Q&A with Alan Moore will be published tomorrow.

Helen Lewis-Hasteley is an assistant editor of the New Statesman. She tweets @helenlewis