Skulduggery Pleasant by Derek Landy, Tom Percival

Meet Skulduggery Pleasant

Ace Detective
Snappy Dresser
Razor–tongued Wit
Crackerjack Sorcerer
and
Walking, Talking,
Fire-throwing Skeleton

—as well as ally, protector, and mentor of Stephanie Edgley, a very unusual and darkly talented twelve-year-old.

These two alone must defeat an all-consuming ancient evil.

The end of the world?

Over his dead body.