These are a few of the mystery authors I have read and enjoyed. I recommend you do as I do, and start with the first book in each series and read in sequence.
Rex Stout--creator of Nero Wolfe and Archie Goodwin; the writer I most admire and would like to emulate; murders abound, but in a lighter vein; if you like this series, several of the stories were made into enjoyable TV shows a few years back starring Timothy Hutton
Jo Nesbo--very dark and gritty Norwegian writer; creator of Detective Harry Hole; Nesbo has no qualms about killing off characters and maiming his protagonist; although the Harry Hole novels haven't been made into movies yet, Nesbo's recent novel "Headhunters"was filmed and it's excellent
Stieg Larsson--a trio of very dark and violent novels featuring Lisbeth Salander, all very well done and made into great films (see the Swedish versions)
Robert B. Parker--creator of private eye Spenser; he gets down and dirty, but there's a lot of humor in Parker's witty banter
James Lee Burke--Sheriff's Detective Dave Robicheaux and sidekick Clete Purcel get into all sorts of scrapes, most based in my home state of Louisiana; Burke's smooth writing style is amazing