I love everything by Fred Vargas, especially the quirky Chief Inspector Adamsberg series. The Chalk Circle Man is the best of the lot.
The Chalk Circle Man is the first book featuring Jean-Baptiste Adamsberg, one of the most engaging characters in contemporary detective fiction.
When strange, blue chalk circles start appearing overnight on the pavements of Paris, the press take up the story with amusement and psychiatrists trot out their theories. Adamsberg is alone in thinking this is not a game and far from amusing. He insists on being kept informed of new circles and the increasingly bizarre objects which they contain: empty beer cans, four trombones, a pigeon's foot, four cigarette lighters, a badge proclaiming I Love Elvis, a hat, a doll's head. Adamsberg senses the cruelty that lies behind these seemingly random occurrences. Soon a circle with decidedly less banal contents is discovered: the body of a woman with her throat savagely cut. Adamsberg knows that other murders will follow.
Vargas' novels have a specific kind of appeal: they are, of course, superbly constructed puzzles, but above all they're wholly original crime novels with a different kind of outlook on the form: they're a bit bonkers, a bit maddening, a lot gripping, and vastly entertaining. They're not for people who demand gritty realism from their crime fiction, but as exercises in the flightful pleasure of reading a crime novel written from a slightly different angle, they are the absolute best you can find. This is a superb first entry in the Adamsberg series.