R
Rick Riordan
The Trials of Apollo
Apollo, cast down as a mortal teenager, must complete dangerous quests to regain his godhood. This series blends humor and Greek mythology as Apollo faces ancient enemies and learns humility. It's a fun read for fans of Percy Jackson's world.

The Hidden Oracle
The Trials of Apollo #1
The Dark Prophecy
The Trials of Apollo #2
Camp Half-Blood Confidential
The Trials of Apollo #2.5
The Burning Maze
The Trials of Apollo #3
The Tyrant's Tomb
The Trials of Apollo #4
Camp Jupiter Classified - A Probatio's Journal
The Trials of Apollo #4.5
The Tower of Nero
The Trials of Apollo #5This series is a direct continuation of the events in the Percy Jackson and the Olympians and The Heroes of Olympus series. Reading those two series beforehand is essential to understanding the character arcs and the status of the world.
All of these series exist within a shared universe where different mythological pantheons coexist. You will find subtle references and occasional character crossovers between this series, The Kane Chronicles, and the Magnus Chase and the Gods of Asgard series.
While the series are designed to be read in their own internal order, the narrative timeline for the Greek and Roman-focused books follows a strict sequence starting with Percy Jackson and the Olympians, followed by The Heroes of Olympus, and then The Trials of Apollo. Other series like Magnus Chase and the Gods of Asgard take place roughly concurrently with the later events of this timeline.