Harry Turtledove has the ability to write a novel of such stunning fiction that it takes your breath away. Unfortunately, he also has the ability to write a novel of such numbing inanity that it, again, takes your breath away. This, however, is one of the former types. The book starts innocently enough, but quickly twists and turns, in characteristic Turtledove style, into a maelstrom of different stories, all weaving together into a cohesive whole.
Very few authors have the capacity to pull so many threads together, but Turtledove is one of them, and he produces his magic with a flourish, as suddenly everything you thought you understood about the plot is turned on it's head and yet another new development is unleashed.
Have you figured out I liked it yet? It was excellent - I would recommend it to anyone who enjoys reading science fiction. I won't use the cliche "impossible to put down", because if you read it without putting it down and thinking about what is happening, you will miss some of the finer nuances in the plot. Well, to be honest, you'll lose some of the major "nuances" in the plot as well :)
In short...
A Very good book. Recommended to all who like Sci-Fi, and Fantasy novels, for that matter. Enjoy.