The Rook by Daniel O'Malley

 This is an interesting riff on an internal (as opposed to international) thriller--the sort of thing where there's some conspiracy afoot that might destabilize at least an important fraction of the government--set in a world where there's magic, where monsters of myth and legend exist, where the governments of at least the UK and the US have small attachments to defend against such things. It's written with verve and wit, and there are some ... interesting Easter eggs for someone with enough knowledge of myth and legend; the story is pretty good, too, though there's some escalation that seems at least mildly implausible, even given the novel's premises, and the deescalation at the end seems likewise from nowhere. While the instigating event has a strong whiff of The Bourne Identity, there's probably a broader debt to Ludlum here: He wrote a lot of novels where some group or other was looking to destabilize some government or another.