"Not his best"
A difficult subject to tackle because of the geographic spread of the action and the constraints of audio in following the action. Built into this genre is the uncertainty over who is an historic personage and who is a purely fictional character. I like Doctorow and thought City of God, Billy Bathgate wonderful novels. The writing in The March was not as rich as in City of God, but it was more than adequate to render the characters and the action. A problem was the absence of historic context - just what was happening elsewhere in the war, what was Grant doing, how important was Sherman's victories, etc.
One final caveat: Joe Morton's narration was not good enough. When de does the characters he's fine; but when he reads the narrator's voice it was dull and not properly inflected in too many places.