The Civil War Era Studies Department at Gettysburg College recently published a list of their top 200 recommended books and articles on the Civil War.
You can see the list here.
It’s an awesome list. While I might have a slightly different list [and only different by one or two volumes in each category], I can’t really argue with the selections here. They did a great job with this, and I highly recommend it for those who are looking for ideas of books to read to learn about the Civil War.