Mortal Coil (Skulduggery Pleasant Book 5), Derek Landy

He’s dead. She’s deadly. The bad guys don’t stand a chance.

The fifth book in the bestselling Skulduggery Pleasant series. Skulduggery and Valkyrie are back – just in time to see their whole world turned upside down. As Valkyrie struggles to protect her dark secret, Skulduggery and their friends are more vulnerable than ever as a plague of body-snatching Remnants are released upon the world…