Harry Turtledove turned his first book I reviewed "How Few Remain" into an 11 book series. For purposes of continiuty, I am going to refer to the next three books in his series as the Great War series.
To make a long story short, the South won the second civil war along with half of Mexico and an amazing alliance with the British.
This is the story of World War 1, where Abraham Lincoln has turned the African American slave population into marxists and they all decide to rebel against the South at the same time the South is pitted against the North in World War 1 again. Several big names from this time period are still around, but in different positions, and the first made up person of the series, Jake Featherston arrives as a Southern Artillery sargeant.
This series perfectly sets the stage for what is to become in the last books with Featherston slowly gaining power and turning Texas into a Southern Auschwitz for African Americans.