The Killing Joke — Anthony Horowitz

When Guy Fletcher scoffs at a feeble joke he overhears in his local pub, he finds himself, in quick succession, head-butted and struck by an idea. Is it possible to trace a joke all the way back to its original source? Guy's meandering trail leads him to a Hungarian dentist, a hyperactive troop of Boy Scouts, a group of giggling grave-diggers, and a half-dozen undercover detectives. He's also sure that he's being followed by a sinister Englishman, Irishman, and Scotsman. He has an unfortunate encounter with a banana peel. And there's a fly in his soup. Guy is on the verge of discovering something very unpleasant. Making jokes is no laughing matter.