The Black Tower by Louis Bayard

Finished The Black Tower by Louis Bayard, a historical mystery set in 1818 Paris and involving the lost Dauphin of France, Louis-Charles (who would have been Louis XVII if Louis XVI and Marie Antoinette hadn't lost their heads in the revolution). The novel also features the historical François Vidocq, a former criminal who became France's first Director of Security and one of the first detectives of the modern era.

The writing is good - 1st person present, which is difficult to pull off but Bayard does quite well with snappy (and often humorously vulgar) dialog, flashbacks, a diary, correspondence, and fast-paced narrative. Got a little long in the middle, as modern novels often do, but the denouement was satisfying. Bit of an anti-religious bias (Bayard writes for Salon after all), but again, it's something many modern novels stumble over. Too bad, decreases their shelf life.