This book was a really good read and has a great premise. I am sure everyone has always wondered at the possibilities of what could have been, how things would be now, and Turtledove does an excellent job portraying this to his audience.
This is Book 2 of the American Empire series. It covers the Roaring Twenties. Most of the original characters from How Few Remain are now gone since it is about 40 years later. If you are hooked on this seris, this is a good read. If you have not read any book in this series, you should begin with How Few Remain and go in order. Otherwise, they are not very enjoyable.