"The Boomer" is a classic.
"Setup Running" BY jOHN w. Orr is not fiction, it is the true biography of John's father running steamers from about WWI until the later 1940s. Well written and easy read. Good steam railroading stories.
"Headlights and Markers" is collection of short RR stories edited by Frank Donavon and Robert Henry. Lost of classic RR fiction writers included.
"Harry Bedwell, Last of the Great Railroad Storytellers" by Frank Donavan is also pretty good.