The author has an incredible imagination ! Making-up stories for the Percy Jackson series already impressed me a lot, but Heroes of Olympus adds even more to the world he builts for his heroes. In the Mark of Athena, the confrontation between Greeks and Romans begins and a long journey awaits the heroes. All seven of them are very interesting and worthy, however Riordan has this thing to allow the reader to have his/her preference. Team Leo for me !