The Trials of Apollo is a popular Rick Riordan sequel series to both the Percy Jackson series & The Heroes of Olympus series. Older elementary readers meet teenage Lester who is actually Apollo, the son of Zeus, who was cast out of Mount Olympus. This book series brings new adventures with familiar characters and the same Percy Jackson Universe. Percy Jackson & The Olympians, The Heroes of Olympus and The Trials of Apollo are all series in Rick Riordan’s Camp Half Blood Chronicles that follow the same group of protagonists.