The Trials of Apollo

The Hidden Oracle is the first book of the series. It is told in first-person by the main character Apollo, and it uses haikus for chapter titles. The book was released on May 3, 2016.[5]

The book opens with Apollo landing in a dumpster in an alley in New York City; in the form of a mortal teenager named Lester Papadopoulos because of the events leading up to the war between the Greeks and the Romans. After shenanigans happen, he meets Meg McCaffrey. Believing that he must only undertake a simple quest to regain his immortality, Apollo and Meg travel to Camp Half-Blood with the help of Percy Jackson, where they learn most of the world's Oracles have stopped working. The two undertake a quest to locate and protect a remaining oracle, also hoping to learn how to help the other oracles and regain Apollo's immortality. Apollo also finds out that the first oracle he has to save is heavily guarded by the mysterious 'Beast' who happens to be the first of the three evil Roman-emperors-turned-Gods, the Roman Emperor Nero.[7]

The Dark Prophecy is the second book in the series. It was released on May 2, 2017.

The book continues the story of Apollo as the mortal Lester, as he leaves the safety of Camp Half-Blood and journeys across North America to restore the remaining four Oracles and learn how to defeat the Triumvirate of Roman emperors-turned-Gods, while being helped by Leo Valdez, Calypso and Festus the bronze dragon, the Hunters of Artemis, and some new characters.[8] Apollo has to face and defeat the second Triumvirate emperor- Commodus, with whom Apollo shares an awkward and regretful past to obtain the Throne of Memory for his next prophecy. Apollo travels to the Oracle's cave and gets his prophecy and comes back and defends himself and his friends from Commodus.

The Burning Maze is the third book in the series. It released on May 1, 2018.[9] The book follows Lester Papadopoulos/Apollo, Meg McCaffrey and Grover Underwood while they try to rescue Herophile, an Oracle that speaks only in puzzles, from the most infamous Roman emperor. After fleeing the labyrinth, Apollo dreams about the Oracle saying that he must save her even though it is a trap. When he wakes up, he finds himself in Grover's base. When Meg wakes up, they find the line from the prophecy, 'Demeter's daughter finds her ancient roots' to occur. Apollo and Grover go out to try to find Gleeson Hedge in an army store called Macro's Military Madness. They then find out that Macro, the store owner, is actually Naevius Sutorius Macro, working for Caligula. He attacks them with an army of automatons. By activating 'command sequence: Daedalus twenty three', they defeat Macro with his own robots. They then navigate the maze with enlisting the help of Piper McLean and Jason Grace.After a raid on Caligula's fleet of ships and Jason dying, Apollo and Meg steal a pair of Caligula's sandals, which let people navigate the Labyrinth. Piper, upset over Jason's death, is unable to help them anymore. The next day, Grover, Meg and Apollo, using Caligula's shoes, walk the Labyrinth. They free Herophile, discover a new prophecy and free Helios. Piper comes back and kills Medea, a sorceress who was working with Caligula (also Helios's grandchild). The book ends with Leo arriving from Camp Jupiter, learns about his friend death, and Apollo and Meg going to San Francisco while Gleeson Hedge, Mellie and baby Chuck, Piper and her dad set off to Oklahoma, with a ride from Leo.

The Tyrant's Tomb is the fourth book in the series. It was released on September 24, 2019. The story is set at Camp Jupiter in the San Francisco Bay Area. The story starts off with Apollo and Meg taking Jason's body to Camp Jupiter. On their way to Camp Jupiter, they are attacked by eurynomos, but a girl with pink hair arrives with dryads and a faun and kills the Eurynomous. She then introduces herself as Lavinia and says she will take them to camp Jupiter. After that, all the dryads and fauns start to leave. But as the last faun, Don, tries to leave, Lavinia spots him and said that he will not leave because of what he is supposed to owe Lavinia for helping him. They carry Jason's tomb to the tunnel where she knows a shortcut to Camp Jupiter. Suddenly, Hazel as well as two more euronymous come. They enter the tunnel, while Hazel tries to kill the euronymous. Apollo tries to sing a song to help Hazel, but is scratched in the belly by a Eurynomous, before Hazel kills it. Due to him being scratched, Apollo starts to turn into a yeet. Hazel sees Jason's coffin and is terrified because she had a dream about Jason being killed by Emperor Caligula. After that, the five carry Jason's tomb and arrive in Camp Jupiter where they are greeted by Frank Zhang and Reyna Ramirez Arellano while everyone watches Jason's coffin being carried. Apollo sings a song about his quest and everyone is touched. They all decide that they will carry on with Jason's plan which was to build temples to honor the gods.

Apollo then faints and has a dream about Caligula and Commodus discussing their plan about either taking Camp Jupiter without conflict, or destroying it using Greek fire explosions by mortars on Caligula's yachts. Apollo finds himself in a bed where Meg explains that he had been asleep for about 1 day and a half. There is a funeral for Jason that night, where Lupa comes and tells Lester to get divine help to defeat their enemies. Apollo and Frank go to Ella and Tyson, who were busy recreating the Sibylline Books. They get a prophecy regarding Tarquin's tomb, as they found about it in the previous prophecy.They later go to the senator where they select him, Meg, Lavinia and Hazel to go to for a mission to find more about the final king of Rome, Tarquin, who has returned. After they find out about the old ghost King and his plans, they get more scared for the camp. They also find that Tarquin has kept the soundless god at Sutro Tower. After they return, they realize that to solve communication issues and get divine help, they need to destroy the soundless god. So a quest is issued for Apollo, Meg and Reyna to go to Sutro Tower. But that is in the evening of the next day, and most of the morning is spent on training. At the tower, they realize the god is Harpocrates, who had troubles with Apollo. He also has a jar containing the voice of the Sibyl of Cumae. With some difficulty, they manage to get the last breath of Harpocrates, along with Sibyl's Jar, which are required to get divine help. As they return, they are ambushed by an euronymous again, and after they manage to kill him, they are helped by Lavinia and her friends, who had escaped from the Camp earlier. Reyna and Lavinia issue "Plan L" to defeat the yachts that Apollo saw in his dream. After Apollo and Meg return, they see the camp in the midst of a war. Apollo calls for divine help on Temple Hill. He decides to call Diana. Frank (the other praetor of Rome) sacrifices himself holding his firewood killing Caligula along the way to save the other legionnaires. Apollo later kills Commodus in the grief of losing Frank. But Commodus gave the order to fire. But due to Plan L, it fails and the yachts are destroyed. Meanwhile, Tarquin had reached the bookshop where the books where being re written, but Ella and Tyson are not there. Meg and Hazel fight Tarquin. Diana finally arrives and kills Tarquin and heals Apollo just in time. Reyna and Lavinia, along with Peaches, return. Arion rescues Frank who mysteriously survives death and Reyna A. Ramirez Arellano pledges herself to the goddess Diana (Artemis) and joins the Hunters. Dakota, son of Bacchus, passes away overnight due to wounds that he got in battle. He was the longtime Centurion of the Fifth Cohort. Don the faun also dies. He gets reincarnated into a laurel tree, Apollo's tree of victory. Hazel is voted as the new Praetor of Camp Jupiter and Lavinia voted as Centurion of the Fifth Cohort.

Apollo receives his old Godly Bow as a gift from camp Jupiter and Meg receives seeds and they set off to New York after receiving the last and final prophecy from Ella and Tyson, which they realize is a terza rima, and they would have to find more stanzas in the East. They go in hopes to once again be reunited with their old friends from Camp Half-Blood.[10]

The Tower of Nero will be the fifth and final book of The Trials Of Apollo (October 2020). Apollo will have to kill Nero, meeting with the python, his old nemesis. Nico and Will are the key to all of it.

A companion book titled From Percy Jackson: Camp Half-Blood Confidential was released on May 2, 2017.[11] It is based on background facts of Camp Half-blood.

The book explores the story of one of the side characters, Lavinia Asimov, through the perspective of her personal diary.