It’s not often that an author described on his own Wikipedia page as “disgracefully neglected” is awarded a €100,000 literary prize. But this is where the Irish author Mike McCormack finds himself, with Wednesday’s announcement that he has won the International Dublin literary award for his novel, Solar Bones. As someone who has hovered close to mainstream success without ever shaking off the slightly damning label of “writer’s writer”, he is unsurprisingly delighted.

“I don’t feel neglected today. I don’t know who put that Wiki page up, but I think whoever did will have to rethink that,” he laughs. “I was shocked. I had completely given up hope that I was going to win it. But I’m over the shock now and enjoying myself – very much.”

The International Dublin literary award, previously known as the Impac, operates with a slight air of mystery: a ridiculously long longlist (150 books this year) is picked by librarians around the world, from Barbados to Estonia, who hand their selection over to a panel of authors to bestow the grand boon on one unsuspecting writer.

Solar Bones is the Galway author’s fifth book, but undoubtedly his most read. “People are looking at me like a debutante,” he told the Guardian in 2017, after he was longlisted for the Man Booker and won the Goldsmiths prize for experimental fiction. “It’s very much what I feel like.”

The International Dublin judges hailed Solar Bones as “formally ambitious, stylistically dauntless and linguistically spirited”. The novel is written in a single sentence that flows over 270-odd pages, and spans a single day: All Souls’ Day, when, according to superstition, the dead can return to the land of the living. It is narrated by Marcus Conway – husband, father, civil engineer, a man gripped by “a crying sense of loneliness for my family” – and a ghost, a factor that, for McCormack, explains the experimental form. (“A ghost would have no business with a full stop,” he once argued. “It might fatally falter and dissipate.”)

To this day, my agent smiles and says, ‘No, I’m not going to tell you how many people turned the book down' Mike McCormack

With literary fiction sales down sharply, some writers have been quick to start clanging the novel’s death knell – against which Solar Bones has been championed as a firm rebuttal. In his review for the Guardian, Ian Sansom said was “destined to be acclaimed by anyone who believes that the novel is not dead and that novelists are not merely lit-fest fodder for the metropolitan middle classes”.

It is surprising then, even to McCormack, that Solar Bones could now be regarded as part of the mainstream. “The publishing industry doesn’t always credit the reading public with being adventurous enough and intelligent enough for certain books,” he says. “And Solar Bones is popular – insofar an experimental novel can be popular. But yes, I did worry, ‘Will anyone read this?’”

At first, it looked like no one would: several publishers “whined and moaned and griped” over its experimental form, its quiet domesticity, says McCormack. “No one wanted it. Two editors at major publishing houses took it to acquisitions meetings but couldn’t sell it because I had no reputation for selling books. They were immediately shut down by the accountants and suchlike. As a commercial proposition, I am a very difficult sell – was a very difficult sell,” he amends. “To this day, my agent smiles and says, ‘No, I’m not going to tell you how many people turned the book down. You know a few – that’s all you need to know.’”

Lisa Coen, one of the two people behind Tramp Press, the tiny Irish publisher that first took the chance on the novel, says: “If you were a cynical publisher and looking to pick a book that wouldn’t lose you money, you probably wouldn’t pick Solar Bones. And it’s lovely that this wasn’t the case. That this prize is decided by readers and librarians is a huge deal for Mike. Mike’s always had a cult following, he gets stopped in the streets. But this is a different seal of approval.”

Coen was tasked with telling McCormack the good news about the Dublin award; he took the call while standing at a Galway bus stop. “And he hung up on me!” she says. “He needed a quiet moment to recover. He aims as high as he can, but he’s astonished when he gets accolades. It’s a lovely quality in him. With the Booker longlisting and winning the Goldsmiths prize, you’d think he’d be a bit out of touch by now, but he was properly blown away.”

Previous winners, perhaps overwhelmed by the sheer size of their sudden bounty, have tended to splash out : Akhil Sharma, in 2016, announced he would buy himself some new shoes (and set up a scholarship to help young Indian women get an education), while José Eduardo Agualusa told the Guardian last year that he would build a library in his adopted home of Mozambique.

What will McCormack do? He thinks it over. “I have a very modest plan: I’m going to buy a chair,” he announces. “The chair I was writing in collapsed under me last night. I turned sideways and it twisted under me. But I might buy an expensive one now.”

Solar Bones by Mike McCormack (Canongate Books, £8.99) is available at guardianbookshop.com.