The Hidden Oracle

The Hidden Oracle is a 2016 American children's fantasy action-adventure middle grade children's fiction novel based on Greco-Roman classical mythology written by American author Rick Riordan. It was published on May 3, 2016, and is the first book in The Trials of Apollo series, the second spin-off of the Percy Jackson & the Olympians series. The book and its cover art by John Rocco were first announced in 2015. It has been published in hardcover, audiobook, ebook, and large-print editions. The Hidden Oracle has been translated into 19 languages from its original English.