I'm on the 15th book already...
This is the second book in the Skulduggery Pleasant Series. From what I can tell, this series isn't one problem or main goal stretched out over multiple books, like Percy Jackson and The Olympians or Heroes of Olympus. Skulduggery and Valkyrie Cain are facing a different villain in this book, (Which *SPOILERS* is understandable, considering the last one exploded) But they still have problems that they were dealing with in the first book that stretch over to the second.
It is really really good.
Go read it.
If you haven't read the first book yet, here is is: TA DA