It's the fifth in a series of excellent (make that superb) volumes on PRR history, by David W. Messer and Charles S. Roberts, and published by Barnard, Roberts & Co., Inc., 2606 Willow Ave., P. O Box 7344, Baltimore, MD 21227, featuring photos, track and signal diagrams, etc., that I don't know how they even found. The books are about 9x12, about 400 or so pages on slick paper. The first 5 volumes I've seen are as follows (I think they're up to VIII now):
I --- Altoona to Pitcairn 1846-1996
II -- Philadelphia to Harrisburg 1828-1998
III - Philadelphia Terminal 1838-2000
IV --Harrisburg to Altoona 1846-2001
V ---Philadelphia to New York 1830-2002
There's one out now on Philadelphia to Baltimore, as well. Lots of historical text as well as good information in the photo captions.