The House of Hades (Heroes of Olympus Book 4) by Rick Riordan

The fourth book in the bestselling spin off series from Percy Jackson and the Olympians, featuring the original hero - now in a brand-new look!Seven Heroes. One Prophecy. Destiny Calls. Lost in the depths of the Underworld, Percy and Annabeth's lives rest in the hands of their friends and fellow demigods - Jason, Piper, Leo, Hazel and Frank. Their five friends must reach the Doors of Death - gateway to the Underworld - if they ever want to see Percy and Annabeth again. But between them and the doors lies a vicious army hellbent on destroying Camp Half-Blood. . .and the whole world with it. If the demigods can fight their way through- and Percy and Annabeth can survive hell itself - they might just have a chance. If they don't. . .Well, it's only the whole world at stake. Return to the World of Percy Jackson in the best-selling, brand-new adventure featuring the original hero in Percy Jackson and the Olympians: Wrath of the Triple Goddess - out now!
Binding: Paperback / softback