Skulduggery Pleasant 6. Death Bringer: Derek Landy

Meet Skulduggery Pleasant: detective, sorcerer, warrior.
Oh yes. And dead.
The Necromancers no longer need Valkyrie to be their Death Bringer, and that`s a Good Thing.
There`s just one catch. There`s a reason the Necromancers don`t need her any more - because they`ve found their Death Bringer already, the person who will dissolve the doors between life and death.
And that`s a very, very Bad Thing...