I am not sure where to ask this question. The question is this, what is the most detailed atlas of the european theater during world war 2? Is this available online or in a book or both?
The ETO was large. Any atlas of the whole area would, of necessity, be limited in its scope. To get more detail you would need to look at individual countries, and even then the detail would not show much. I have seen maps of individual actions that are quite detailed, but don't show much about what was going on elsewhere.. What exactly do you need?
a map of that shows the big red one's route through europe basically. is there a map like that somewhere?
Very basic. From: The First! The Story of the 1st Infantry Division: WWII G.I. Stories Booklet (Lone Sentry)
Takao is right. The map shows the route, but not the many engagements they were involved in. If you would start doing that, you would find the scale increasing dramatically.
I'd suggest a Michelin map of France . Add to this the Belgium one , you"ll certainly have parts of Germany , including Aachen. Another suggestion might be the liberations maps issued by Michelin which precisely retrace the battlefields. A third one is the detailed APEX