Zeus is angry at Apollo for a variety of reasons, most notably for the younger god's allowing his Roman descendant Octavian to rise to power during The Heroes of Olympus series by giving him his blessing.

Lester (Apollo) must meet some new friends and train at Camp Half-Blood, save and return 5 undiscovered oracles that have gone dark, and get back to his true form. The series follows the trials of the god Apollo, who has been turned into a mortal named Lester Papadopoulos as punishment from his father and king of the gods Zeus. The fifth book in the series, The Tower of Nero, was released on October 6, 2020. The fourth book in the series, The Tyrant's Tomb, was released on September 24, 2019. The third book in the series, The Burning Maze, was released on May 1, 2018. The second book in the series, The Dark Prophecy, was released on May 2, 2017. The first book in the series, The Hidden Oracle, was released on May 3, 2016. A supplementary book, Camp Jupiter Classified, has also been released in addition to the main series. It is set in the same world as Riordan's Percy Jackson and Heroes of Olympus series and the references to characters and happenings from earlier stories prove this. The Trials of Apollo is a pentalogy of fantasy adventure and mythological fiction novels written by American author Rick Riordan that collectively form a sequel to the Heroes of Olympus series. Print ( hardcover and paperback), audiobook, e-book

The hidden oracle