The first book in the Heroes of Olympus series:
"Three new demigods. One missing hero. A curse that threatens to destroy them all."
Jason wakes up in a bus of Wilderness School students on a field trip. He's disoriented and confused - he's lost all of his memories, suddenly has a girlfriend named Piper and a best friend named Leo, and the only thing he knows for sure is that something is very, very wrong.
Piper struggles with a secret, and she has no idea what's gotten into her boyfriend Jason - why can't he remember her? As a freak storm hits the bus and unleashes terrifying monsters, she's spirited away to a camp for demigods with Leo and Jason.
Leo finally feels at home after being welcomed at Camp Half-Blood, but his strange day just keeps getting weirder. The camp's inhabitants seem convinced that they are all children of Greek gods and goddesses, and keep insisting that he's one of them.
Narrated by 3 new demigods, this thrilling return to Percy Jackson's world will take them on a quest to find Hera, queen of the gods, who has been captured by the titans. They will go on to find old friends and new, while also trying to puzzle out the meaning of the Prophecy of Seven...
Rick Riordan - Heroes of Olympus: The Lost Hero