OK, to get farther afield with historial fiction, I highly recommend Harry Turtledove's books, which are alternate history. The Guns of the South is of course the classic, telling the story of what might have happened if the South had been provided with AK-47s during the Civil War. The WorldWar/Colonization series is a supremely engrossing series about what might have happened if aliens had invaded in around 1942. (sounds silly, but it's really quite good.) The Great War series, beginning with So Few Remain is a story arc of what might have happened had the South won the Civil War (but lost The Great War), with it evolving into a close analogue of Nazi Germany. What makes these books so fascinating is that Turtledove goes inside the minds of historial characters to tell the story. Of course, there are also characters that are entirely fictional who play pivotal roles, but many of the main characters are historical.
