Four authors on this one - count 'em! Three take on the task of creating the 39 clues back story on three important characters. The last moves forward the story from the first 10 books. It all works and is well paced, giving this series a fresh new road to careen down. Rick Riordan is most certainly not done with this series and (see any of my previous posts on him) I hope he continues to get help from his friends.