In a shocking turn at Tuesday’s Costa Book Awards ceremony, Nathan Filer took the overall prize for his debut novel, The Shock of the Fall.

Filer’s victory upset expectations for a win by Kate Atkinson, who was widely expected to take the U.K. prize for Life After Life. Atkinson won the Costa, then known as the Whitbread, for her first novel, Behind the Scenes at the Museum, in 1995. The overall winner is awarded £30,000.

The Shock of the Fall, inspired by Filer’s decade of work in mental-health services in Bristol, U.K, is published in North America by St. Martin’s Press under the title Where the Moon Isn’t. It tells the story of a young man’s descent into schizophrenia.

In a statement, jury chair Rose Tremain said that Filer shows “very keen powers of observation” resulting in a first novel that is “astonishingly sure-footed.”

“We felt that to have taken such a marvellously well-articulated thing and brought it to life in the way that he has is an extraordinary achievement,” said Tremain.

The previous debut novel to win the award was Stef Penney’s The Tenderness of Wolves in 2006.