The Sea of Monsters
Rick Riordan
Seventh grade has been surprisingly quiet for Percy Jackson. Not a single monster has set foot on his New York prep-school campus. But when an innocent game of dodgeball among Percy and his classmates turns into a death match against an ugly gang of cannibal giants, things get...well, ugly. And the unexpected arrival of his friend Annabeth brings more bad news: the magical borders that protect Camp Half-Blood have been poisoned by a mysterious enemy, and unless a cure is found, the only safe haven for demigods will be destroyed.
Very fun read that picks up where the last one left off. A good one that will have you waiting for the 3rd one.