Color me late to the party, I suppose; most people read this 15 years ago. I had a rough introduction to Turtledove, though, and it took me several years to get over it and decide maybe I should, before giving up on him entirely, try some of the stuff he was actually famous for rather than just the bits of his work that I stumbled across at random. And what do you know - this is actually really good alternate history. I suppose I shouldn't be surprised by that. After all, while he certainly didn't invent the subgenre, he's written dozens of them, and is widely considered a master of the concept.
Plot-wise, the point of divergence in this universe involves the Earth of 1941 being invaded by the Race, a bunch of lizard-like conquerors with a remarkable inability to conceive of things different from themselves, which, along with humanity's unanticipated speed of innovation and adaptation, turns out to go quite some way toward offsetting their overwhelming technological advantages. The slowness of development of their own species as well as those previously conquered led them to anticipate no appreciable changes between their reconnaissance in the 13th century AD and their arrival 800 years later...
As I may have mentioned in the past, I love a good alternate history (though often avoid reading them because good ones are rare and bad ones are painful), and so I enjoyed the hell out of this one, despite it possessing no shortage of the awkward writing and poor character portrayal that has bugged me about Turtledove in the past. This time, the concept/setting/plot was good enough that I was able to overlook the writing, and indeed it didn't even register until I'd read about 90% of the book. I hope this trend continues, because if I continue to be able to overlook Turtledove's prose shortcomings in favor of his alternate-history strengths, I'll suddenly have rather a lot more alternate history available to read.