The Battle of the Labyrinth (Percy Jackson and the Olympians #4)
by Rick Riordan
I enjoy each Percy Jackson book, but this has been my favorite to date.
As always Percy Jackson goes on another fun, exciting adventure!
I was glad we finally know how Annabeth came to be as it always bugged me that Athena had children when it's common knowledge that she's one of the virgin goddesses. The "meeting of minds" to bring about a brain child amused me, but I also like the whole idea. :D