Worldwar by Harry Turtledove (1995, Hardcover)

Did you read my review on the 1st book in this series? No? GO back and read the review on "In The Balance".
This is a continuation of the Alien invasion of Earth during WWII. Since the aliens did not expect any kind of technology here they came with minimal equipment to take up over before the colonization fleet arrives. Having already Nuked Berlin they now nuke Washington in an attempt to get us to give up. They have never come across a race quite like humans though, where we fight harder and learn to adapt very quickly (they take their time studying something for a long time before trying it). Who ever heard of a race that would figure out how to make a jet fighter based on the parts they find and then fly them with no real testing? And which country managed to steel enough uranium and figure how to make one of those bombs the aliens used on us? You will have to read this great alternate history/SciFi book and find out!