The Sea of Monsters (Rick Riordan)

This is the second installment in the Percy Jackson series. Percy's friend Groves is in big trouble, and it will take everything he and Annabeth can do to save both their friend and all of Camp Half-blood.

The camp is in utter chaos when one of their long-standing defenses begins to fail. Everyone will be killed unless Percy and Annabeth can retrieve the golden fleece from Polyphemos (a giant Cyclops), which just happens to be in the middle of the Sea of Monsters (commonly known as the Bermuda Triangle). One disaster after another awaits them in this portion of the sea, but it is their friendship that keeps them pressing on. A new characters introduced in this book is Tyson, a young Cyclops. It is difficult to determine whether he is friend or foe, and as Percy figures that out, he reveals some interesting pieces of his character and his relationship with Annabeth.