I just started reading this, and it is without doubt, some of the best SF I've come across. It's an alternate history of World War II- what if an alien a race had chosen this time to invade, forcing the Allies and the Axis to ally against the greater foe? The concept seemed a little corney to me at the bookstore, but all of that evaporated at the first page. Turtledove's worldbuilding is brilliant- just enough to explain things wihout hammy up the story or bogging down the narrative. I was just wondering if anyone else had come across this.