Solar Bones by Mike McCormack was named the winner of the £10,000 award, which recognises fiction “that breaks the mould”.
Published by Tramp Press, the novel follows the recollections of an engineer named Marcus Conway briefly returned from the dead.
Notably, McCormack is the third Irish writer to win since the prize began in 2013.
Chairman of judges Professor Blake Morrison said: “Set over a few hours in a single day, and told in the first-person voice of a middle-aged engineer, Mike McCormack’s Solar Bones transcends these seeming limits magnificently.
“Politics, family, art, marriage, health, civic duty and the environment are just a few of the themes it touches on, in a prose that’s lyrical yet firmly rooted.
“Its subject may be an ordinary working life but it is itself an extraordinary work.”