The Indigo King is by James A. Owen. The third book in The Chronicles of the Imaginarium Geographica. John and Jack are mystified when they discover an ancient manuscript with a warning to them from their friend Hugo, who isn't a caretaker. As they try to discover the meaning of the warning, Hugo accidentally travels back in time and changes the future. Now Jack, John, and their friends must travel through time themselves to correct his mistake. Followers of this series will love this third installment.
Ratings: 7th grade - 9 out of 10.