Please, please, please, please, please, please read Jim Thompson. This guy is a feckin' genius. He wrote in the '50s and is the King of pulp fiction. This guy was writing about the sociopath and the psychopath before anyone knew what these characters were about. His books are always from the criminal's point of view and are so god damned dark that they'll chill you to the bone. If you're a fan of intelligent crime novels, you'll not put the books down until the last page. Especially brilliant are Pop 1280, The Killer Inside Me and the Getaway. Look him up on ebay and take a chance (WHAT'S A FEW QUID?). If you like Cain or Hammett you'll adore Thompson 'cause this guy really takes things to another level.
Otherwise, Edgar Allan Poe for sheer gothic horror. Also, try Franz Kafka's short stories. The longer novels are also good but can be a tad annoying after 100 or so pages.