Camp Jupiter Classified: A Probatio’s Journal is a companion book under The Trials of Apollo. It is structured as a diary that tells the story of Claudia, a legacy of Mercury and Probatio in the Fourth Cohort. It is set to be released May 5th, 2020.
- A sneak peak of the book was present in the Barnes & Noble edition of The Tyrant's Tomb.
- The book is is set to be released the same day as Sal & Gabi Fix the Universe.