The Laughing Policeman by Maj Sjöwall and Per WahlööRead about the other entries on the list.
Sjöwall and Wahlöö set the standard for Scandinavian noir, and also for brooding, flawed Scandinavian detectives. Unlike most of his Anglo-American counterparts, Martin Beck — in true socialist-democracy style — enlists other detectives to help him solve his cases. You eventually come to admire Beck, even if you don't like him.
--Marshal Zeringue