For reasons I can’t fully explain, I’ve become a fan of alternate histories. I’ve read several about the events surrounding World War 2, but the first I’d read about the American Civil War was Ward Moore’s “Bring the Jubilee.“
Its subtitle gives its premise away: “What if the South had won the Civil War?” Written in 1953, it’s probably quite innovative in terms of its concept, but it didn’t really pick up much steam until the last tenth of the book.
I’d still recommend it, though. I’m a sucker for those “What If…?” books, but anyone curious about history could enjoy it.