I often like his stand alone books best, Guns of the South (the southern states win the war thanks to a gift of some handy AK47 from some timetravelers but what are their goal?), A Different Flesh (no homo sapiens entered the americas but some Homo Erectus did) and these are what the colonists meet when they arrived. His series often start well but go on a bit too long. His World War series is ok. WW2 is in full force when aliens invade, then he likes to play with southern Victor. In How Few Remain the South win the war in 62 and then from there on two american states exist side by side and are not friends . A History described in American Front, Walk in Hell and Breakthroughs. He also wrote a book about how the japanese won a much more decisive victory in Pearl Harbour than what happened. The japanese can successfully invade Hawaii. Days of Infamy is that one called.I've read the name, but haven't read anything written by him.
Your mention of Turtledove reminded me: abut a month ago I had a dream that my husband and I were sitting in some living room discussing Harry Turtledove's books with Mr. and Mrs. King, which is weird because 1) I've never read anything by him and 2) my husband rarely reads fiction at all Dreams are weird.