Gives a perspective I've not seen before
Makes it readily apparent why certain battles were fought and what the generals were thinking. Sherman's March to the Sea, my God, you really see the perspective on that.
The North lost of 700,000, the South over 600,000. What a devastation and a waste. One wonders what our world would have been like had the Civil War never happened. We're almost back there; though this time it's going to be a class war, not a territorial one.