Thirteen Bullets — Sean Danker

In this raucous new book in Ralph Compton's Gunfighter series, the only thing Dan Karr can't shoot down is his suspicion about the man who's paying him.
 
George Kingsley has more money than sense, and when he's in trouble he turns to the infamous gunslinger Dan Karr for protection. Dan reluctantly accepts, and he kills every would-be assassin without hesitation or remorse. He's superstitious, not sentimental, but Kingsley has kids, and Dan doesn't want to see any child grow up without a father.
 
As the killers keep coming and the bodies stack up, it becomes clear that something is very wrong. Luck favors the prepared, and Dan starts to realize just how little he knows about the family he's risking his neck for. He's always been good at dodging black cats and broken mirrors, but he's spent enough time around gamblers to know that a hot streak can't last forever. Sooner or later, every man's luck runs out...