At the opening of this book, we find Percy at the ROMAN camp, where he is running from some evil gorgons who JUST WON'T DIE!!!! Literally. Percy has seen them dissolve into sand time after time for the past three days, but nothing has happened.
This book is set eight months after the last one, The Lost Hero. Percy has finally woken up from an eight month nap and is on his way to Camp Jupiter, like the Roman version of Camp Half-Blood, where everyone is Roman. Percy believes that he is the son of Neptune, instead of the son of Poseidon, because of course the Romans have no idea that the Greek aspects of their gods still exist and continue to have kids.
Percy meets two new friends: Hazel, daughter of Pluto, and Frank, son of Mars and distant descendant of Poseidon (yes, Poseidon, not Neptune). They also meet Reyna, the leader of Camp Jupiter, daughter of Bellona, and Octavian, Roman aurgury (like the Oracle but less accurate), pain in the backside, son of Apollo (?). And 200 other campers, which I won't name, because that would be a pain, and I don't know all their names.
Nearly straight after he arrives, there is a message from Mars (Ares) and Juno (Hera) saying that Percy and two others need to go on a quest to Alaska, beyond the power of the gods. Percy, being Percy, accepts and along with Frank and Hazel, sets off to fall to his death (again), nearly drown in muskeg (quicksand type thing), and fight giants and Titans. I mean, this is Percy we are talking about people! The action never stops!
This is another amazing book delivered by Riordan, and I definitely recommend it. It leaves you wanting more and more! I know when I finished this book, and I found out that Mark of Athena wasn't coming out for AGES, I was like NO! But it's out now, but it's even more horrible because now I have to wait ANOTHER YEAR before House of Hades comes out!!!!