The Heroes of Olympus

The novel begins by introducing Jason Grace (son of Jupiter), Piper McLean (daughter of Aphrodite) and Leo Valdez (son of Hephaestus), three newly discovered demigods who travel to Camp Half-Blood in response to a prophecy, they set off on a quest to prevent the rebirth of the giant king Porphyrion and rescue Piper's father, who has been kidnapped by another giant, Enceladus. Jason, who has amnesia, also begins to remember pieces of his past throughout the book - most importantly, that he comes from a Roman camp for demigods. Camp Half-Blood resolves to seek out this other camp both to gain allies in the fight against Gaia, the giants' mother and commander, and to locate the missing demigod Percy Jackson, the son of Poseidon.

The novel opens with Percy Jackson (struck with amnesia) discovering Camp Jupiter and meeting several Roman demigods. After a prophecy from Mars, he, Frank Zhang, and Hazel Levesque travel to Alaska to stop the rise of the giant Alcyoneus and free the god Thanatos, whom the giant has captured. After successfully completing their mission, the group returns to Camp Jupiter to defend it from yet another giant, Polybotes, and his army. After repelling this invasion, the demigods from Camp Jupiter go to meet the delegation from Camp Half-Blood arriving in the flying ship known as the Argo II.[7]

After the Argo II unintentionally fires on Camp Jupiter, the seven demigods of the "Prophecy of Seven" - Percy Jackson, Annabeth Chase, Hazel Levesque, Frank Zhang, Jason Grace, Piper McLean, and Leo Valdez - rush to escape the angered Roman campers. They travel to Rome following the Mark of Athena, a magical talisman designed to lead children of Athena (like Annabeth) to the missing Athena Parthenos. During their journey, they hear that Nico di Angelo has been captured by the Aloadae, and go to rescue him. Although they successfully free the son of Hades and locate the statue, Annabeth and Percy are pulled into Tartarus, and Nico promises Percy to get the other demigods to the "Doors of Death".[8]

In Tartarus, Percy Jackson and Annabeth Chase travel towards the "Doors of Death" (the only exit to the mortal world) with help from Bob the Titan, hoping to escape and simultaneously stop more monsters from getting through. In the mortal world, the remaining demigods search for the mortal side of the Doors to help open them. They also meet with Reyna Avila Ramírez-Arellano, a Roman demigod; she, Nico di Angelo, and Coach Hedge leave with the Athena Parthenos for Camp Half-Blood. Once reunited, the original seven sail for Greece, where they expect Gaia's main force will gather.[9]

While Reyna Avila Ramírez-Arellano, Nico di Angelo, and Gleeson Hedge travel towards Camp Half-Blood (where the Romans are preparing to attack the Greeks), the seven of the quest travel to Athens. With help from the gods, the demigods defeat the giants in Athens. They then return to the fight on Long Island and Leo Valdez sacrifices himself to defeat Gaea and restore peace. In the final pages, Leo is resurrected by his bronze dragon Festus and goes to find his crush Calypso. Unaware that he is alive, Camp Half-Blood and Camp Jupiter mourn his loss, determining to become allies and prevent such a deadly war from happening again.[10]

Released August 14, 2012,[11] The Demigod Diaries is a collection of short stories. Similar to The Demigod Files, it contains some new stories with character interviews, illustrations, puzzles, and a quiz. The four stories include:

• "The Diary of Luke Castellan": Thalia Grace and Luke Castellan meet Halcyon Green, Luke receives his knife, and the pair encounters Annabeth Chase. The events of the story take place roughly five years before The Lightning Thief, the first book of Percy Jackson & the Olympians.[12]
• "Percy Jackson and the Staff of Hermes": Percy Jackson and Annabeth are sent by Hermes to retrieve his caduceus from the fire-breathing giant Cacus. The story takes place between The Last Olympian and The Lost Hero.[12]
• "Leo Valdez and the Quest for Buford": Jason Grace, Leo Valdez, and Piper McLean confront a group of Maenads while searching for Buford the table, who has run off with an important piece of the unfinished Argo II. The story takes place at Camp Half-Blood between The Lost Hero and The Son of Neptune.[12]
• "Son of Magic": Alabaster Torrington, a demigod son of Hecate who fought on Kronos's side, finds himself in a fight to the death with Lamia. He is alone after being banished from Camp Half-Blood following Kronos's defeat in The Last Olympian and asks the mortal Howard Claymore for help. This story, deemed non-canonical to the series itself by Rick Riordan, with the events depicted being directly contradicted in The House of Hades and The Blood of Olympus, was written by Riordan's son Haley Riordan.[13][12]

• Percy Jackson: The 17-year-old (in The Trials of Apollo) son of Poseidon from Camp Half-Blood, Percy is the narrator and main protagonist of the preceding series Percy Jackson & the Olympians. In The Son of Neptune, he is depicted fighting amnesia, during which his only memory is his girlfriend, Annabeth Chase.
• Annabeth Chase: Annabeth, 18 years old (in The Trials of Apollo) and a daughter of Athena, is credited as "the smartest girl in camp" by Percy Jackson, a comment that is true and well-deserved. She is a gifted and dedicated architect as well.
• Piper McLean: A 16-year-old (in The Trials of Apollo) daughter of Aphrodite. She is one of the few children of Aphrodite who have the rare hereditary gift of "charmspeak" (the ability to magically convince people to do what the person in question says) and is described as beautiful by Jason Grace. She carries a knife called Katoptris (previously owned by Helen of Troy) that shows her visions of the future. She begins dating Jason Grace (son of Jupiter) during the series.
• Leo Valdez: A 16-year-old (in The Trials of Apollo) son of Hephaestus who can summon and control fire (a very rare ability). He is famous among his cabinmates for repairing the automated bronze dragon Festus gone wild, who had given more experienced campers life-altering disabilities. He leads the building of the Argo II.
• Nico di Angelo: A 14-year-old (in The Trials of Apollo) son of Hades. Born in the 1930s in Italy, his father Hades sent him and his sister to the Lotus Hotel and Casino, that sucked them out of time for decades, so he only feels and looks 14. He was the only demigod who knew about both Camps before the war.
• Gleeson Hedge: A middle age satyr, formerly a coach at the Wilderness School. He comes with the seven on the Argo II as their self appointed chaperone.
• Thalia Grace: Thalia is a 23-year-old demigod hunter of Artemis, so she physically appears to be about 16. She is Jason Grace's biological sister, but a daughter of Zeus rather than Jupiter (Jupiter and Zeus are the same god in different aspects, making Jason a child of Rome and Thalia a child of Greece).
• Tyson: Tyson is a young cyclops, the half-brother of Percy. He loves peanut butter and is the boyfriend of Ella the harpy.
• Rachel Elizabeth Dare: Camp Half-Blood's oracle. Rachel is not a demigod or a legacy; she is a regular mortal human who was born with the gift to see through the Mist. She is the current Oracle, being a vessel for the Spirit of Delphi.
• Grover Underwood: Percy's best friend, a satyr; he and Percy have an empathy link that allows them to sense one another. Also, Grover Underwood is gifted by the lord of the wild, Pan.

• Jason Grace: A 17-year-old (in The Trials of Apollo) Roman son of Jupiter who can fly, control winds and lightning, and create storms. He is a natural leader and was praetor before Hera took his memory and sent him to Camp Half-Blood.
• Hazel Levesque: A 14-year-old (in The Trials Of Apollo) daughter of Pluto. She originally lived in the 1940s before dying to stop the rise of Alcyoneus and later being revived by her half-brother Nico di Angelo. She can control precious metals and stones, navigate underground, and manipulate the Mist.
• Frank Zhang: A 16-year-old (in The Trials of Apollo) son of Mars and a descendant of Poseidon on his mother's side. Frank can shapeshift.
• Reyna Avila Ramírez-Arellano: An about 18-year-old (in trials of Apollo) daughter of the Roman goddess of war, Bellona. Reyna can lend her useful abilities (like her courage, strength, and leadership ability) to other demigods.
• Octavian: An about 18-year-old Roman descendant of Apollo, he serves as the Camp Jupiter's augur. Octavian is power-hungry and seizes control of the camp after Reyna goes looking for the Athena Parthenos. He is largely responsible for the Roman Camp attacking Camp Half-Blood.

The Lost Hero was a number one bestseller on the lists of The New York Times,[22] USA Today,[23] The Wall Street Journal,[24] and Publishers Weekly.[25] Many critics praised the novel as a good follow-up to Riordan's previous series. Despite this praise, some reviews were more mixed. Vicky Smith of Kirkus Reviews wrote, "There are far too many pages of stretched-out action, telling not showing and awkward dialogue... Unless Riordan tightens things up considerably by number five, readers may find themselves hoping that it does not end with a third Great Prophecy".[26]

The Lost Hero won the Barnes & Noble Best Book of 2010 award and was a Massachusetts Children's Book Award Honor book for 2014, among other honors.[27][28] Rick Riordan was named "Author of the Year" for the novel at the 2011 Children's Choice Awards.[29][30] The book was also recommended by the ALA Best Fiction for Young Adults list of 2012.[28][31]