Turtledove is good. He is a history professor in addition to an author of alternate history/science fiction works.
A classic alternate history on the victory of the South is Bring the Jubilee, by Ward Moore. The hero, who lives in a world in which the South won the Civil War, travels through time and brings about an alternate history in which the North won at Gettysburg. This might be hard to find. You might have luck using www.bookfinder.com.
If you are interested in the Confederate navy, there is a new book out about the CSS Shenandoah, a Confederate commerce raider that fired the last shot in the Civil War. One of the authors is a descendent of the captain or first officer. The book is Last Flag Down, by Baldwin and Powers. (Powers was co-author of Flags of Our Fathers,)
If you can find a copy in a library, Memoirs of Service Afloat by Raphael Semmes, commander of the Alabama, tells the story of that CSS raider and is full of flaming Southern nationalist rhetoric.
How the heck did “Bring the Jubilee” go out of print? It’s one of the seminal works of alternate history....