My Pennsylvania RR books include the following:
Pennsy Power I and II by Al Staufer.
Pennsylvania Railroad-1940s-1950s by Don Ball.
Pennsylvania Diesel Years by Robert Yanosey.
Pennsylvania Electric Years by William D. Volkmer.
I enjoy running both the scale and semi-scale GG I, K4s, GP-9, E-8, and last but certainly not least Lionel's iconic Post-War Pennsylvania S2 Turbine of which I have several.