Stiletto is the second book in the Rook series by Daniel O’Malley, and you should read both of them because they are awesome. The series tells the story of the Checquy, a secret agency within the British government that deals with strange happenings and unusual people.
When there's trouble who do you ask? Is one of the children in the neighborhood school spontaneously teleporting back to the hospital where he was born? Get the Checquy. Have fast growing crystals suddenly enveloped a house, entombing the family inside? Call the Checquy. Has some monstrous, unknown animal washed ashore after a run-in with a boat propeller? Call a marine biologist. Does this creature have a person implanted in it’s head? Call the Checquy.
You might well think that a secret government agency that deals with these sorts of things would be really, really cool. After all, some agents have superpowers! They use their superpowers to fight monsters!! But agents of the Checquy aren’t just super-powered, black-leather-wearing-monster-fighting badasses, they are also government agents. They’ll fight monsters. But as government agents they first have to finish some important paperwork. Lots of paperwork. For example, the car with dark tinted windows they drove at improbable speeds to reach and and fight the monster? They had to park it in a metered space. So they’ll need receipts. Parking isn’t cheap and these are government agents on government salaries, who need receipts if they are going to be reimbursed for anything.
Stiletto picks up where Rook left off, but focuses on two new characters: Felicity and Odette. Felicity is an agent of the Checquy. She’s stuck on a diplomatic mission, acting as Odette’s bodyguard. Odette is a member of the Grafters, a family of body-modifying super surgeons who have been fighting a secret war for years with the Checquy. There have been horrible losses and hard feelings on both sides of this conflict. So, even though both Odette and Felicity want peace, there are factions in the Checquy and the Grafters that would do anything to restart this bloody, violent war. Luckily Felicity has superpowers, and Odette has advanced surgery skills, plus an implanted venom gland, and a propensity for attracting trouble. Can the two women work together to bring peace to their respective organizations? Can they save London? Can they manage not to destroy each and every formal gown they own? Fighting monsters is surprisingly messy.