I am looking for the best and most thorough books about the Wehrmacht and Germany's general military effectiveness during WWII. Thanks in advance!
Robert Citino has some books you may find worthwhile:
The German Way of War: From the Thirty Years' War to the Third Reich is only partially about WWII, but it does a good job busting the blitzkrieg myth and putting the German doctrines of 1939-1945 in context with previous wars.
The Death of the Wehrmacht: The German Campaigns of 1942 and The Wehrmacht Retreats: The Campaigns of 1943 focus only on single years, but they vividly explain how things fell apart for the Wehrmacht.