We return to Camp Half Blood with Percy Jackson and his gang of awesome misfits! I love how this series focuses on a new quest every book. The missions are always different but they tie so well into the series creating a great flow for the storyline. 
 Artemis, The Huntress, saves Percy and Thalia from a monster attempting to capture other demigods they're trying to recruit. She's the leader of a pack of wild girls who are immortal as long as they forsake love and desire of men. Artemis has to leave her girls behind though with Percy and the other campers at Camp Half Blood when she has to go on a hunt of her own. That's when we meet Apollo, Artemis's brother, who is kind enough to drop everyone off at Camp Half Blood in his sun chariot. 
 The Oracle's mission: To save Artemis from whatever danger she's in with both Hunters and Half Bloods uniting for a common cause. It turns out though that Annabeth is in some trouble of her own also and needs help along the way. 
 Nemean Lions, evil skeletons, and more ! On a cross country adventure to reach San Fransisco in time before the winter solstice. 
 (view spoiler)[Nico = Son of Hades! So all three big Gods did have a child(ren) even though warned not to because the prophecy! Though the children of Hades were in a time loop casino that we experienced last book (great tie in!) so technically he didn't break the promise. Nico is mad though about his missing sister Bianca and I have a feeling is going to want revenge after Percy broke his promise to protect her. (hide spoiler)] 
 Another thing I love about this series is how Percy ages every book. Every year he's a bit older and a bit wiser in his decisions. He's still only fourteen in this book but he's made major improvements in character development since the first book.