Ta-Nehisi Coates has this to say about it:
They need to make people read MacPherson's history of the Civil War in order to vote in this country. I don't think I've read an 800plus page book that moved so smoothly. This is the greatest work of history I've ever had the privilege of reading.
So many of the things that make us Americans are (still) tied up in the Civil War, and about how we're still dealing with a lot of the same issues and same rhetoric after 150 years. At this point of my life, I've begun to see the wisdom in Faulkner's "the past is never dead, it isn't even past" quote, but never has it been illustrated as effectively.
And reading the new afterword as it examines "positive liberty" and "negative liberty" within the context of the war and American society was fascinating.