HOW big is your imagination? What's the biggest story it can control? Try this. A motel on the edge of the Mohave desert.
An American couple checks in, him a second- generation Indian maths whizz from Baltimore, her a Jewish-American editorial assistant from New York, both of them with nerves frayed from looking after an autistic four-year-old. Among the other guests, a British rock star trying to clear his head.
Too small-scale? Look again at that motel, at the three-fingers of rock on the horizon above it. At the cracked walls of the nearby UFO Diner, built in the shape of a flying saucer. There's a history to this place, if you can imagine it: all the way back to the native indian tribes, to the Catholic missionaries roaming west of the Colorado in the 18th century. And wider, and deeper too.
So now what you've got isn't just a story about a fractious, worn-out married couple or a drugged-out rock star. It'll creep back into all of the pasts that there ever have been on this dusty, liminal patch of the planet. To that time when the woman who runs the motel joined the hippies at their out-of-town camp by the rock pinnacles. To the people on that site before them who were convinced that benign visitors from outer space would arrive soon and put the world to rights. To the native Americans, hunted down first for their land and then by anthropologists for their stories. To the myths they told, of wily coyotes and places where the living could almost touch the spirit world.
There will be Indian runners, 19th-century Mormon miners, hubristic Wall Street masters of the universe and 1950s guilt-ridden aircraft engineers who have been chosen by enlightened aliens to spread the word of their existence among humankind. There may even be an abduction.
With almost any other writer you could think of, all of this would be wildly excessive, unbelievable. With Hari Kunzru ("like the young Martin Amis, only nicer" – Carol Ann Duffy) it's the novel which, of the four he's written, most closely matches what he hoped it would be when he started out, the one which most clearly delineates his passions.
Gods Without Men started as a short story, something to take his mind off the fact that the novel he was working on wasn't going anywhere. Which was a bit embarrassing, given the fact that when he applied for a year's fellowship at the New York Public Library in 2008 the notion of using its Asian collection to help him write a novel set in 16th-century India had been a key part of his proposal.
Up to then, Kunzru's career had been going effortlessly. His 2002 debut novel, The Impressionist, won him a 1 million-plus advance, and for once it wasn't a curse: critical acclaim (a prize or a place on the shortlist of almost every literary award going) was matched by excellent sales, a pattern that continued with his next two novels, Transmission (2004) and My Revolutions (2007). By then, he was already on Granta's Best Young British Novelist list, a bright, principled, poster-boy for sassy, multicultural Britain.
Yet there he was in New York, with a new novel that had just fallen apart in his hands. "I'd completely underestimated the effect of moving cultures. America was impeding me from thinking properly about this book about India. There I was in this office in this beautiful marble-filled building in midtown Manhattan with all the resources that any writer could possibly wish at my fingertips – and no project. So when some friends in LA said they were going on a road trip to Joshua Tree and the desert and asked me along, it seemed to make sense."
Kunzru had been to Death Valley once before, when he couldn't get a flight back from California to London for a full week in the aftermath of 9/11 and decided to go there instead. There was something that drew him to the desert, to its empty horizons, thin air and unfiltered light.
The more he fell under the spell of the American desert – and in the three years since 2008 he's made about seven trips there, from the northern Nevada to southern New Mexico – the more he realised how other people had too. At Giant Rock, a seven-storey boulder near Landers, California, he found out about the German prospector who lived in an underground cave and was killed there in a 1942 police siege when suspected of being a Nazi spy. Then aircraft engineer George van Tassel moved in to live in the cave. In 1951, van Tassel had a vision of beautiful Nordic aliens coming out of a spacecraft and giving him the secret of how humans could extend their life. It was the start of the UFO boom. Both men's stories went into Kunzru's notebooks, and, slightly changed, into his novel,
"I was fascinated by all of that, and by the life extension machine van Tassel built, the Integriton. I always thought that this was something that came out of the Cold War, but actually a lot of the first generation of people who claimed to have contacted UFOs belonged to the older spiritualist tradition, of theosophy, Mme Blavatsky, the mystic Order of the Golden Dawn, that kind of thing. And you notice that the first generation of alien visitors were always higher beings who only wanted good things for Earth. It's only in the late 1950s when someone reported the first abduction experience that you see these classic grey, almond-eyed aliens.
"What happens then is that you get the idea of there being a cosmic war between the Nordic 'good' aliens who are into the idea of healing the world and the grey aliens who aren't. And I began to realise that there was a strand of quite spiritualist UFO people who wanted to get in touch with the first lot. Often it's not that they've seen a machine coming down from the sky but that they have received psychic transmissions from some grand master – at first from Venus, but from further and further away the more we explored space."
Kunzru edged towards his novel by starting off with a short story about the couple in the desert motel. "I realised I had a novel on my hands but didn't know where it was going to go. So I thought, I'm going to do everything that you're not supposed to do when you plan a novel, I'm going to step back and let this thing take itself wherever it wants to go and I'm not going to worry about how things connect until later on.
"Why I am excited about this is that it became a working method, not to force closure on anything. I had a bit of a fight with my editor on this, but I love the book's fragmentary nature. These days we're all hyper-aware of the canonical way in which stories are supposed to play out – people are taught all about three-act scripting and where to put the reversal and all of that – and I think we can do more interesting narratives."
Not all loose ends, he says, need to be tied up: in fact, it's oddly liberating when they're not, when there are are gaps between stories as large as those in Robert Bolano's monumental novel 2666. "Because that's just like the human experience – we don't have complete explanations for everything and we don't always get closure."
An obvious comparison among novels by Kunzru's contemporaries is David Mitchell's Cloud Atlas. Certainly there's the same mastery of different registers, the same confident interleaving stories between decades and even centuries. But Kunzru's novel doesn't play around with genre as ostentatiously. However varied his subject matter – and it ranges from weird-but-true desert war games to a pin-sharp satire on social networking – there is also almost always a strong underpinning sense of place.
His love of the American desert, he says, isn't just something he is parading because Gods Without Men is set there: he'll carry on going back even when it's nothing to do with his writing. Perhaps, he muses, it's because he is a European: historically, Americans have under-appreciated the desert in their midst, dismissing it as an annoying interruption en route to Palm Springs, Phoenix or Las Vegas, a place where bad things happened before civilisation triumphantly burst westwards to complete America's manifest density.
Despite the influence of the conservationists and the Sierra Club, some of that negativity still lingers. It's Europeans who have nothing to compare with the abstract landscape of the Nevada salt flats, European film-makers such as Wenders and Antonioni who fall in love with the lunar landscape of the Mohave desert (the long opening tracking shot in Paris, Texas, the unearthly emptiness of the vistas in Zabrinskie Point). For all the Californian utopians, the young people and artists who go on occasional retreats there or stage festivals like the Burning Man in Nevada, the American desert is, Kunzru says, "weirdly underdescribed and underloved". He can't understand that. The desert has always been the place for deep thought – for gods without men, in the Balzacian quote that gives the novel its title – but is also, he notes, a place where he seems almost inevitably to stumble upon weirdness. On that first trip in 2008 with his friends, "next to a few Ballardian ruined motels" around a failed desert resort by Salton Sea, he came across a hermit living in a fire truck who has made it his life's work to paint a whole mountainside to the glory of God; on later trips he saw the Integriton, the machine that ufologist George van Tassel built under instruction from aliens to extend human life, and met Iraqis who are paid to act out various roles as civilians in fake villages for US Marines war games.
"The more I went into the desert, the more there seemed to be something inexplicable and unexplained hiding behind the corner of everything. And the stories all had this quality to them, that they'd turn into something we couldn't easily grasp. It's as if you have the impossible erupting into your work – yet somehow it all makes sense."
You could say exactly the same about Gods Without Men. And because Kunzri has learnt that you don't always have to explain everything, sometimes the impossible really does seem to happen, sometimes it might just be a desert mirage.
But sometimes – and for his readers, these are the best moments, and there are plenty – you just can't tell the difference, no matter how hard you look.
• Gods Without Men by Hari Kunzru is published on 4 August by Hamish Hamilton, price 12.99. He appears at the Edinburgh book festival on 14 August.