The Heroes of Olympus, Book Three: The Mark of Athena: The Graphic NovelBy: Rick Riordan Series: The Heroes of Olympus The third exciting entry in Rick Riordan's best selling Heroes of Olympus series is now a graphic novel! In The Son of Neptune, Percy, Hazel, and Frank met in Camp Jupiter, the Roman equivalent of Camp Half Blood, and traveled to the land beyond the gods to complete a dangerous quest. The third book in the Heroes of Olympus series will unite them with Jason, Piper, and Leo. But they number only six who