There are certainly the outer trappings of westerns--train robberies, shoot-outs, bandits, and so forth--but the story itself is essentially a vengeance-driven mystery. Gil Denning, for five years, has made a living as a bounty hunter, though he cares nothing for the money it brings in. The only thing he wants is information on the train robbers who, through collateral damage, killed his wife five years earlier, less than a month into their marriage. The mystery arises in that he has no idea who they are--nor does anyone else, until similarities to the crime arise during the course of events in this novel--and he has spent all this time desperately seeking any scrap of information he can find.
The novel reads more like a P.I. story than a western as Denning collects information through informants, bribery and occasional violence, is repeatedly the target of violence himself by people worried he's getting too close to his goal (which would endanger the criminals' current plans, of course) and has not one, but two women (a squeaky-clean angel and a beautiful, but fallen, angel, naturally) fall head over heels for him. But Gil Denning has no time or interest in romance. Vengeance is his only concern.
As I said, I loved the novel. The western elements are mostly cosmetic, but it's a good solid mystery with enough clues that you can figure out the ending by yourself if you're paying attention, although there was one red herring towards the end that made me doubt my (ultimately correct) conclusion for a little while. There's also plenty of action--both the two-fisted and shooting kind--to keep your interested if mysteries aren't your thing.
If you are a hardcore western fan, it might not be your cup of tea, as it doesn't feel like most of the westerns I've read, but if you're a fan of two-fisted, hard-shooting crime stories, I definitely recommend it.