Another good book is "INVASION They're Coming!" by Paul Carrel. It tells the story of Normandy and the 80 days battle of France following from the German point of view.
One of the lines in it has stuck with me. On seeing the Americans continuing to land in the face of the defensive fire, the author states "I realized then that the war was lost...You could not get Germans to do that!"
Another example of some Germans seeing the reality comes from a book I no longer remember the name of, but it was written by a German about the DAK, and specifically the final months. I remember he recounted an incident around the time of the Kasserine pass fighting, some Germans overran a US command post, and among other things, they captured the units mail.
In that mail was a package, a birthday cake, sent from the States to one of the soldiers, and still fresh enough to eat.
The author commented on how, at that point, he realized they could not win the war. If the Americans had the capacity to send a birthday cake to a frontline troop AND it arrived still fresh enough to eat, he knew Germany could not match that. He was quite envious of America having that much capability. He said we didn't use it well, and at the time, he was right, but he knew we would learn, and in that, he was also right. We did learn and the more we learned, the better we got.
Yes, we also kept making tons of mistakes, but as the Axis found out, the more we practiced, the better we got.