This is one of the most ambitious books I've read in recent memory. The plot is built like a Russian doll -- subplots nested within subplots, in a very methodical way. Each subplot happens in a different period, and the writer really differentiates the language well, writing in a different register for each period.
This is an engaging read. It's got some historical fiction, some Sci-Fi, and lots of political commentary. Somewhere near the end it starts feeling just a tad didactic and too direct, but I still enjoyed it.