Scepter of the Ancients (Skulduggery Pleasant)

Scepter of the Ancients (Skulduggery Pleasant) by Landy, Derek. paperback edition. ISBN: 9780061731556.

Stephanie led a pretty quiet existence until her uncle died. Not only did he leave her his mansion, he left her a new best friend—Skulduggery Pleasant, a skeleton detective (sorry, a supernatural skeleton detective)—who waltzes into her life for keeps. Now shes acquiring magical powers, endangering her life to fight evil, and trading snappy comebacks with something without a body. So much for her quiet existence. Stephanies big job is to find the Scepter of the Ancients—a weapon capable of destroying anyone and anything—before the evil Faceless Ones steal it for themselves. She just has to defeat a bunch of ghouls, kick the butts of a clan of vampires, and hide her powers from the entire world (oh, and her parents). No worries. Shes got a bunch of bones on her side.