Much of the info and photographs from the 1935-1945 era that I have in my library are found from sections of books dealing with much larger time periods. Three books that deal with this era specifically are:
RAILS ACROSS CENTRAL NEW JERSEY by Benjamin L Bernhart with photographs of Ralph E Halloek (Outer Station Project, 2010)
A more recent publication, it is short on text, but has very rare wartime photographs from 1943 around Central New Jersey (see map on cover) on the CNJ, Reading, B&O, and LV. These interesting photos, printed on glossy paper, are mainly of steam locomotives and their trains in action and give a good sense of the railroading in this era. 96 pages.
RAILROADS AT WAR by S Kip Farrington Jr (Samuel Curl, 1944)
An old printing, original right from World War II, the author was an expert of contemporary railroading who wrote many books on the subject. The writing style is casual. Some the many topics covered (25 chapters) include troop trains, fast freights, CTC, the challenge of moving war traffic, modern steam locomotives, and the coming of the diesel-electric; all illustrated through period railroads. In spite of the old printing, there are many fine photographs (taken by legendary photographers) of railroads all over the U.S. and all are reproduced on nice gloss paper. 320 pages.
THE IRON HORSE AT WAR by James E Valle with the photographs of Jack Delano (Howell-North Books, 1977)
Also of early 1943, this book features photos taken by Jack Delano from his epic journey documenting railroads and railroading during the War for the U.S. Office of War Information. The text is ok, but the photos are super and again add to an understanding of what it was like then. 256 pages, gloss paper.