Every Bet’s a Sure Thing (Mac Detective Series #2), by Thomas B. Dewey (epub/Kindle/pdf)
"Thomas B. Dewey is one of detective fiction's severely underrated writers!" -- Bill Pronzini
In his second adventure, Mac is hired to tail a mother and her two kids on the train from Chicago to Los Angeles. All is going well until he is thrown off of the train -- while it's moving at high speed!
"Mac has been called one of the most believable and humane PI's in crime fiction. He is reluctant to use either his gun or his fists, but will do so when the situation demands it, or in self-defense; he doesn't merely solve his clients' cases, but provides moral support and sympathy as well; and perhaps most notable of all, Mac feels, and is not afraid to show itópain, loss, sorrow, loneliness." --thrillingdetective.com