Secret societies using Babbage Engines to predict and manipulate history are accidentally exposed, launching a war of spy-vs-spy, with a few intrepid folks caught in the middle. Sort of a cross between Asimov's Foundation series and a spy novel, with a long academic supplement at the end on the use of statistical methods for predicting historical trends.

A must read for the STS crowd. A weak conclusion, and the heroine's definitely in Mary Sue territory, but Flynn pulls off this blend of adventure and academia.