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. It is set in the same world as Riordan's Percy Jackson and Heroes of Olympus series and references characters and happenings from earlier stories. A supplementary book, Camp Jupiter Classified, has also been released in addition to the main series. The first book in the series, The Hidden Oracle, was released on May 3, 2016. The second book, The Dark Prophecy, was released on May 2, 2017. The third book, The Burning Maze, was released on May 1, 2018 The fourth book, The Tyrant's Tomb, was released on September 24, 2019. The fifth book in the series, The Tower of Nero, was released on October 6, 2020. Source: Wikipedia (en)