In these masterfully conceptualized alternate histories (it even says so on the cover), Turtledove transcends dull academic studies and finally asks a good question: What would happen if an alien invasion interrupted WWII? Suddenly, weather patterns and MRE nutritional content (hobby horses of military historians) are secondary to the dangers of Lizard soldiers and someone apparently named "Big Ugly." Facing extinction, the Axis ally with the Allies in a grand alliance whose sole allegiance is to defeat the intergalactic invaders. Will our warmblooded forefathers emerge victorious? What kind of friendships will blossom between previously sworn enemies and how will this impact world peace? Will an aging Einstein's command of physics make him a super-ace pilot who can curve bullets and open black holes at will? I don't know, but you could embrace the alternate version of your life where you do. This set contains all four books in the Worldwar tetralogy, and the binding on each is sound.