I don’t think Harry Turtledove is a very good alternative history writer, because what he’s usually doing is just telling the original history but with the names and serial numbers filed off, assuming that our history’s OTL will stil happen even though there’s been some big change: the American Revolution never happens, but Martin Luther King still becomes a leading political figure; the South wins the Civil War but WWI and the rise of Hitler are still going to happen just in the U.S; the Great Depression is going to happen in 1929 regardless of the policies of the government of the U.S at the time; the east coast of the United States is a giant island in the middle of the Atlantic, but George Washington still leads a rebellio against Great Britain, and so on.
He also has a tendency to rely on very outdated history in somewhat troubling fashion – one short story of his is grounded in the idea that Lincoln’s lenient Reconnstruction policy would have prevented violence in the South (when Johnson’s quite similar policy led to huge amounts of violence in the South) and that the “harshness” of radical Reconstruction is to blame for enduring radical tensions. Which was the dominant historiographical view in the 1950s, but has been discredited since the 70s/80s.