I'm just starting Harry Turtledove's In At the Death

It's the 11th in a series that asks What if the South had won the American Civil War. The series began in 1880 with the CSA purchasing Sonora and Chihuahua from the Empire of Mexico to extend their influence to the Pacific... and sparking the Second Civil War. How Few Remain

This book is set in 1944. Yes, WWI and WWII and the time between... all looked at as if the USA was split in two. He paints an interesting picture... and he uses imaginary events to make commentary on our historical perspective.

In addition to fictional characters, he sets well know historical figures into unlikely situations... No Lincoln assasination, Custer never fights the Indians..., Patton is a southerner of course, and Douglas McArthur never goes to the Pacific.

It's a strong 6 unless you really enjoy stories set in alternate timelines. In that case it's an 8.