<Tr> <Th> Preceded by </Th> <Td> The Heroes of Olympus </Td> </Tr> <P> 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 other Riordan tales, and references characters and happenings from earlier series . A supplementary book has also been released in addition to the main series . </P> <P> The first book in the series, The Hidden Oracle, was released on May 3, 2016 . The second book in the series, The Dark Prophecy, was released on May 2, 2017 . The third book in the series, The Burning Maze, was released on May 1, 2018 . The fourth book in the series, The Tyrant's Tomb, will be released in Fall 2019 . </P> <P> The series follows the trials of the god Apollo, who has been turned into a human as punishment from his father and king of the gods Zeus . Zeus is angry with 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 . The final book of The Heroes of Olympus, The Blood of Olympus, takes place about six months before the beginning of The Trials of Apollo . </P>

When is the 4th trials of apollo coming out