The Lost Hero introduced some fun new characters, namely Jason, a Roman transplant to Camp Half-Blood who can't remember anything from his past; Piper, whose father has been kidnapped and to save him, she must betray her friends; and Leo who has a way with tools and fire (Leo was by far my son's favourite because of his quirky humour).
The mystery surrounding Jason was really fun. I love the Roman elements and having them play off of the Greek elements of the book. There were also some great twists and turns that kept me and my son on the edge of our seats. The book is also full of action - fighting, adventures, dragons, evil monsters, and inuendo of even worse things to come...
The story is told from all three characters points of view. Each character took turns for 2 chapters at a time. This was good because it really allowed us to get into the heads of the different characters. I also think this widens the appeal to both boys and girls because there are more chances of relating to a character.
If you've read the Percy Jackson series, you will enjoy revisiting Camp Half-Blood and some of the characters from that series. I love the set up of how the new characters will eventually intermingle with the original characters, but at the same time, this is a whole new adventure.