Skulduggery Pleasant is like reading the secret dream of a bored teenager... imagine that one day you found out that you're descended from ancient sorcerers and have powers of your own, and that there's a mysterious benefactor willing to take you on as an apprentice in this whole new world. That's what happens to the protagonist, and she seizes the chance. Adventure and some hilarity ensue.
This book is advertised as being targeted at pre-teens and teens... but it's entirely accessible for grownups both in story and language. I really, really enjoyed it.