When I first read this I was surprised because Alistair Maclean had written Cold War thrillers, novels located in Arctic locales, some contemporary novels and some with World War II in the background. This was his first, and only, venture into the American West.
Always thought this was one of his best novels. After this, the author sadly began to decline. But in "Breakheart Pass" his prose was still sharp and so was his plot. As in many of his novels, his characters are on a ship or outpost or, in this case, a train and a number of mysterious deaths occur. Clearly one or more of the characters are killers.
This was made into a movie with Charles Bronson and it's one of the few MacLean books that Hollywood didn't screw up. That's probably because MacLean wrote the script and it adheres closely to the novel. A very suspensful tale. In his prime there was no one better than MacLean. The novel is a fitting tribute to the old West.