The novel is the seventh entry in his Jackson Lamb series about disgraced MI5 spies. Mick won £3,000 and an engraved oak beer cask at the annual Harrogate crime writing festival, which runs until Sunday at the Old Swan Hotel in the North Yorkshire town.
The author, 58, said: “It’s a privilege and a delight to win Theakston Crime Novel of the Year.
“I can’t think of anywhere I’d rather spend the early part of summer than at Harrogate.”
The Lamb novels have proven very popular and were recently turned into a TV series, starring Gary Oldman as unpredictable spymaster Lamb alongside Kristin Scott Thomas.
Simon Theakston, executive director of sponsor T&R Theakston, said: “Mick Herron’s Slough House manages to combine intrigue, peril and humour in a deft exploration of international espionage.”
Express editor-in-chief Gary Jones said: “Once again, it’s a huge pleasure to be associated with the world’s most famous celebration of crime writing.
“Our congratulations to all the shortlisted authors and especially overall winner Mick Herron.”
A highly-commended gong was awarded to Joseph Knox, 35, for his tense thriller True Crime Story, which blends fact and fiction in the story of a missing student. He said: “It’s a weekend I’ll never forget.”
A special presentation was also made to US crime fiction legend Michael Connelly, author of the popular Harry Bosch and Lincoln Lawyer novels, who won the Outstanding Contribution to Crime Fiction 2022 award.