There are a number of first person accounts of working on the railroad and the PRR in particular which I've found to be a good read.
The Brasspounder - Sanders - telegraph agent PRR
Firing on the Pennsy - Dietz - fireman PRR
Long Island Railroad Memories - Harrison - engineer - PRR
The Mightiest of them All - Kraft - fireman WWII PRR
No Royal Road - Custer - 19th Century PRR - Altoona - this is an autobiography - first third of the book PRR specific
Voices of the Pennsylvania Railroad - Loeb - general accounts of workers on the PRR
Three very good books (they are long but well written) about construction of freight cars, passenger cars, and locomotives are the books by White
The American Railroad Freight Car: From the Wood Car Era to the Coming of Steel
The American Railroad Passenger Car
A History of the American Locomotive: Its Development 1830-1880
For a good overview of the impact of the railroads on the United States I'd recommend
All Aboard! The Railroad in American Life - Douglas