So this is the third book in the INCREDIBLE Percy Jackson series by Rick Riordan, Percy Jackson and the Titan’s Curse. I would definitely recommend this for all ages.
The gods and demigods all know that the titans are rising, and the it is only a matter of time before the Great Prophecy is fulfilled. Percy, Annabeth and Thalia are sent to a military school, Westover Hall, to rescue to young demigods before the manitcore gets to them. Unfortunately, the extraction goes wrong, which ends up with Annabeth being taken by the manticore. Artemis also ends up getting kidnapped by Luke, so Hunters and Campers join forces on a quest to save Artemis from Luke and the Titans.