Daniel O'Malley's debut novel covers some familiar ground, but the reason I'm picking it as today's OTILT is because it manages to wring something new from that familiar ground, and the result is an exciting fantasy thriller that mixes the modern espionage genre with the sort of magical world posited by the "Harry Potter" books. It's an intriguing collision of genre, and it works far better than I would have guessed just from reading the synopsis.
From the very beginning, the book takes a fresh perspective to tell the story, with Myfanwy Thomas "waking up" inside her body, completely unaware of who she is or how she's gotten into the situation where she finds herself, surrounded by dead bodies in a park in London. It's not quite a "Bourne Identity" situation, since the Myfanwy that wakes up is not the same person who was attacked, and she has to figure out how she ended up in this body. Thankfully, the old Myfanwy (pronounced "Miffany," according to the narrator) knew that something cataclysmic was coming, and so she wrote herself a series of notes so her new inhabitant could pretend to be her and solve the mystery of how this identity exchange took place.
What she learns is that she is a Rook, and she works for an organization that handles any and all supernatural invasions or disturbances in England. There are two Rooks in the organization, and a handful of other positions, and as many agendas in play as there are other employees. The other Rook is a four-bodied identity named Gestalt, for example, and Myfanwy finds herself hard-pressed to maintain the illusion that she is this person who she never met.