The House Of Hades

In Rick Riordan's fourth novel of the Heroes of Olympus series, Percy and Annabeth journey through tartarus and encounter many trials including a room too evil to look at, an attack by Empousi and Tartarus himself. Meanwhile Leo, Hazel, Frank, Jason, and Piper are being pounded on the boat, The Argo II, By rock monsters. After that they have to fly half-way across the world to stop Gaea's forces from leaking out of the doors of death. Will the Argo II's crew pull through and get to the doors of death in time to save Percy and Annabeth and survive? Or will Percy and Annabeth disintegrate into nothingness? Find out in The House Of Hades! Awesome recommendation.