The Titan's Curse (Percy Jackson & The Olympians, book 3) by Rick Riordan, 2007

When Percy, Thalia, and Annabeth head to a military academy in Maine to rescue Grover who's in trouble rescuing a pair of half-bloods, they run afoul of Dr. Thorn, a manticore (a poison-dart throwing man-lion) and cross paths with Artemis, goddess of the hunt, and her maiden Hunters. Annabeth is captured, and Artemis leaves on a quest to track down a mysterious beast who may prove the downfall of the gods. But in Percy's nightmares, their dooms are linked. Without Blackjack, his mobster pegasus friend, all might be lost indeed. Adolescent love and angst clash spears with titanic forces in book 3, which nicely escalates all the prior tensions, and shows more depth and heart without sacrificing its breathless excitement or nutty humor. Strongly recommended.