The House of Hades is the fourth book of the series. Annabeth and Percy end up in a pit that leads straight to the Underworld. They need to fight their way through Gaea's forces, find the Doors of Death and seal them both ways in order to prevent the giants from raising the Goddess. One problem: if The Doors are sealed, how will Annabeth and Percy get out?
The other books in this series are the following:
The Lost Hero
The Son of Neptune
The Mark of Athena
The Blood of Olympus (to be released in October 2014)
READ THE FIRST CHAPTER OF THE HOUSE OF HADES HERE!!!!
HEROES OF OLYMPUS OFFICIAL SITE.
This year also marks the release of Percy Jackson's second film adaptation: Percy Jackson: Sea of Monsters. Trailer below!