The Lost Hero, by Rick Riordan, Hyperion, 2010.
About eight or nine years ago, I had the privilege of meeting Rick Riordan and hearing him speak. He was intelligent, articulate and funny -- just like his writing. Percy Jackson was just starting to take off, so he probably had no idea how popular he would become, or that he would need to write a whole new series. But he did write (more than one series). This, the first book of his second series is intriguing, engaging, and fun, from start to finish.