The best source for beginning to end regarding the "Third Reich" is very simple:
"The Ride and Fall of the Third Reich", written by William Shirer
No other source, at least contemporary, covers the material in depth as he does. Lots of good information!!! I reference my copy, the same one that was used as a textbook in college quite a bit. Much of the sources for that book are actual German political and military sources printed by the German government.