Jack Reacher series by Lee Child

Killing Floor
First in the series introducing Jack Reacher, a casualty of the Army's peace dividend who's drifted into town idly looking for traces of a long dead black jazzman. Not only do the local cops arrest him for murder, but the chief of police turns eyewitness to place him on the scene, even though Reacher was getting on a bus in Tampa at the time. Two surprises follow: The murdered man wasn't the only victim, and he was Reacher's brother whom he hadn't seen in seven years. So Reacher, who so far hasn't had anything personal against the crooks who set him up for a weekend in the state pen at Warburton, clicks into overdrive.

Banking on the help of the only two people in Margrave he can trust—a Harvard-educated chief of detectives who hasn't been on the job long enough to be on the take, and a smart, scrappy officer who's taken him to her bed— he sets out methodically in his brother's footsteps, trying to figure out why his cellmate in Warburton, a panicky banker whose cell-phone number turned up in Joe's shoe, confessed to a murder he obviously didn't commit; trying to figure out why all the out-of-towners on Joe's list of recent contacts were as dead as he was; and trying to stop the local carnage or at least direct it in more positive ways.

This was a very intense, complicated and gritty thriller. Lots of carnage mostly at the hands of Reacher as it is "kill or be killed" and he never hesitates. I will probably read more of this series but spread it out a bit as the violence is graphically described.