* AbandonShipping: Quite a bit after the last two books. [[spoiler: Nico coming out as gay/bi and his ShipTease with Will caused most fans to abandon the popular Nico/Rachel and Nico/Thalia pairings. (Ironically them being eternal maidens ''didn't'' deter shippers.) Leo and Calypso becoming an OfficialCouple also killed off a lot of Leo/Reyna, Leo/Piper and Leo/Thalia fans, though there are still some out there.]]
* AlternativeCharacterInterpretation: Hera/Juno. Her characterization in this series as TheChessmaster differs quite a bit from in [[Literature/PercyJacksonAndTheOlympians the previous one]]. Though this is actually literal, considering that the gods change to suit their culture. Juno is LITERALLY Rome's AlternativeCharacterInterpretation of Hera.
** Zeus/Jupiter. For the first four books of the series he's portrayed as having his head up his ass regarding the Gigantomachy. In ''Blood of Olympus'' he makes a reasonable claim that he was trying to avoid locking the demigods into undesirable fates by holding off the Prophecy of Seven. Of course, this doesn't stop him from misappropriating blame when it comes down to it.
*** Like most things with this version of Zeus the excuses sound good until you really look at it. Several of the giants had already risen before Zeus closed off Olympus and Apollo has no control over when prophecies are spoken making the war inevitable. Zeus is using this to try and avoid the fact his pride was hurt that mortals saved the gods from the Titans and he was trying to say the gods did not need mortals. If they had followed Zeus' "do-nothing plan." The gods would have made no preparations and been destroyed.
* AntiClimaxBoss: All of the giants, every single time. Despite the claims of being a greater threat than the Titans they lack the divine forms or magical powers of the Titans or Gods save for a few special abilities. Each one tends to be defeated by one or two demigods with only a god needed to finish them off. In the last book, [[spoiler: despite being together and at full power, the seven demigods would have stood as strong chance of winning if not for the giants brand of immortality and the whole fight turns into a CurbStompBattle once the gods show up.]]
* AuthorsSavingThrow: From the previous series, no less. Nico's actions toward [[spoiler:Percy]] in ''The Battle of the Labyrinth'' seem much less like a hastily Subverted CreateYourOwnVillain subplot [[spoiler:and much more representative of his romantic feelings]] after reading ''The House of Hades''.
** ''The House of Hades'' itself, which irons out some inconsistencies in the previous books, gives the new characters some much needed development, and includes a vast number of references to the previous series.
* AwesomeArt: Some of the cover art looks really, really nice. Particularly ''The Mark of Athena'' and ''The House of Hades''.
* BrokenBase: Rather predictably, the reception of the final book, ''The Blood of Olympus'', has been divisive in the fandom. There are just as many people who enjoy it and see it as a good finale to the series with some points to be wrapped up in later stories as people who hate how it was handled and/or have their expectations let down by it.
** The general lack of focus on Percy and Annabeth in ''The Blood of Olympus'' has caused this reaction. Some think it's Riordan pissing on his two best and most popular characters; others think that the spotlight was better cast on the new characters, Nico and Reyna in particular, especially considering Percy and Annabeth [[Literature/PercyJackson had their own series already.]]
** The way that Nico's [[spoiler:feelings for Percy]] were handled in the final book also had mixed reception. While fans appreciated that his subplot got resolution and [[spoiler:he did get a happy ending, as well as ShipTease with another character]], roughly just as many fans thought he and Percy needed more interaction and the way Nico [[spoiler:chose to move on from Percy]] was a particularly poorly done form of ShipSinking akin to how Percy/Rachel was handled in the [[Literature/PercyJacksonAndTheOlympians previous series]].
* BigLippedAlligatorMoment: The karpoi scene in ''Son of Neptune.'' "Schist!"
* CriticalResearchFailure: Minerva was in fact a very important and powerful goddess in the Roman pantheon. She formed the Capitoline triad with Jupiter and Juno and shared Athena's warlike character -- as one can see from the statues. She did get Medicine and Poetry and Music added to her attributes though.
** Otis and Ephialtes were not originally part of the gigantomachy, although later writers like Ovid did include them. So it's literally a case of DependingOnTheWriter.
* CompleteMonster: ''Bryce Lawrence.'' Arguably to a fault, as his sadism and extreme arrogance are his only real traits as a character. He takes great pleasure the suffering and agony of others, especially if it is unjust.[[spoiler: When he captures Reyna after overhearing her confess to killing her father (except not really), he seems downright ''giddy'' about the prospect of her being tied into a sack with a dog and thrown into a river, the punishment for patricide in Ancient Rome. Not that he doesn't get his comeuppance - Nico ''forcibly turns him into a ghost'' and sends him directly into the Fields of Punishment.]]
* DieForOurShip: Piper and Reyna for some of the Jason/Reyna and Jason/Piper fans respectively.
* EnsembleDarkhorse:
** Leo in ''The Lost Hero'' was shilled as 'the sidekick' and not as important as Piper and Jason. Reviewers described him as the only reason they kept reading.
** Khione.
** Nico, too, carrying over from the previous series.
** Bob/Iapetus.
** Many felt the Giants were having a tough time filling the shoes of the Titans... Then we met the one good giant, Damasen. He kicks ass.
* EvenBetterSequel: The series falls into this pattern: ''Mark of Athena'' is this compared to ''[[{{SurprisinglyImprovedSequel}} The Son of Neptune]]'' with the seven finally uniting and Percabeth back together. Then general consensus has ''The House of Hades'' pegged as an improvement on Mark of Athena, due in no small part to excellent character development, a truly ''insane'' ChekhovsArmory pulling from pretty much every corner of the story so far (think Bob and Calypso), and the journey through Tartarus everyone had been waiting for.
* FanPreferredCouple: Leo/Piper and Jason/Reyna have pretty big fanbases.
** TheReveal that [[spoiler:Nico had a crush on Percy]] in ''The House of Hades'' has given [[spoiler: Percy/Nico]] quite a popularity boost.
** Calypso/[[spoiler:Leo]] has also garnered a lot of fans, thanks to ''The House of Hades''.
*** And as of ''Blood Of Olympus'' has become an OfficialCouple.
** As of ''Blood of Olympus'', many fans have jumped ship to [[spoiler: Nico/Will]].
* FoeYay: [[spoiler:Khione]] is pretty interested in Jason. Jason, on the other hand, not so much.
** There's also Leo's even more obvious interest in Khione.
* GeniusBonus: Midas' line about an oracle in Omaha was a sly reference to Warren Buffet.
** The failed expedition to Alaska was led by a guy named Varus.
** Frank is given a spear tipped with a dragon's tooth. In certain myths, whenever a dragon's tooth was planted, it grew a warrior, so anyone familiar with the myths would have caught the purpose of the spear instantly.
** When mentally listing off punishments from Camp Jupiter, the last item Hazel lists is tying someone into a sack of weasels and tossing them into the Tiber. This one seems to have her especially distressed. In RealLife, the Romans used this punishment specifically for [[spoiler: matricide]].
* GrowingTheBeard: It's widely agreed that the series really hit its stride in the ''The Son of Neptune'' and continued on from there, but special mention has to be made for ''The House of Hades'', where CharacterDevelopment comes out in force and [[spoiler:the first LGBT character in the Camp Half-Blood verse, Nico,]] is revealed, a step of maturity ''no one'' expected to be ever stated outside of WordOfGod.
* HarsherInHindsight: All the way from the original series. In ''The Last Olympian'', Annabeth nearly falls off the edge of Olympus, and Percy catches her and manages to pull her up with help from the others. [[spoiler:This is very hard to read after the events of ''Mark of Athena'' where once again, Percy and Annabeth are dangling over an abyss, and no one can help them up. Rather than drop her, Percy lets go and they ''both'' fall into the ''depths of Tartarus''!]]
** Also hard to read is back in ''The Lightning Thief'' when the flying shoes nearly drag Grover down to Tartarus. They realize that the shoes were meant for Percy and share an "I don't want to even think about it" moment when they realize the only thing that saved them was Grover's hooves. [[spoiler:Guess they weren't so lucky the second time, huh?]]
** Pretty much all of [[spoiler:Nico]] and Percy's interactions after [[spoiler:TheReveal that Nico had a crush on him. It sheds a whole new light on Nico's anger.]]
* HilariousInHindsight: A powerful AmnesiacHero being best friends with a smaller, wisecracking MotorMouth? [[ComicBook/TransformersMoreThanMeetsTheEye Nope, not ringing a bell]].
** In House of Hades, Frank jokes that if they find Octavian they should [[spoiler:load him into a catapult and launch it.]] Guess what happens to Octavian in The Blood of Olympus.
* HoYay: The scene in ''The Blood of Olympus'' where Piper cups Annabeth's face and [[HeadbuttOfLove leans their foreheads together]] to calm her down.
* InstantExpert: Percy and Annabeth had to go through a significant learning curve spanning several years to become as badass as they are now. The main characters of the Heroes series are able to become just as powerful in less than a week.
** Averted with Jason because he's been training at the Roman camp since he was two, and still has his skills even if he doesn't remember how he got them. Ditto with Leo too, kinda, as it seems that Hephestus' kids are gifted with using machines the way Percy's gifted with sailing ships, plus he straight out admits he's a poor fighter and uses his wit or intelligence to get out of most situations. But true for Piper, especially considering her mom's Aphrodite, who's tied with Demeter for second in least warlike of the gods, Hestia being first (in their Greek forms, anyways).
** It's even still kind of averted in Piper's case too. Almost all of her power comes from charmspeaking, and that's something she's been using for years, albeit without exactly knowing how or why it worked. Her charmspeaking did get more powerful over the course of the book, but it wasn't something she just discovered she had and instantly became an expert in. Played straight with her apparent prowess at wielding daggers, though, such as her slicing up Earthborn with no problem or bringing her dagger to Drew's throat blindingly fast. Even then Piper was still using her charmspeak, specifically she use it to make the Earthborn stand still to allow her to cut the monster up.
** In this same vein, Hazel's power over metals and precious gems is something that she worked on for most of her life, ditto for her riding skills, and she trained at the Roman Camp for a year so can fight decently but not up to the level of Percy, Annabeth or Jason. Frank plays this pretty straight though, [[spoiler:with his ability to be good at whatever he wants.]] Though to be fair that relates only to his [[spoiler: shapeshifting abilities]], his archery is also something he's been practicing for years and he admits he can't fight well with a sword or spear; though he could hold his own, it's not up to the level of Percy or Jason.
* JerkassWoobie: Nico. He's of the JerkWithAHeartOfGold variety and has gone through one heck of a TraumaCongaLine of a life, but it must be said he still is extremely icy and pushes people away rather emphatically, often treating the people who try to understand him with hostility.
* LauncherOfAThousandShips: For being 'the seventh wheel', Leo sure gets around a lot in the fandom. Leo/Piper, Leo/Reyna, Leo/Thalia, Leo/Hazel... And those are only the well known examples.
* LGBTFanbase: Following [[spoiler:Nico's outing.]]
* [[MagnificentBastard Magnificent Bitch]]: Annabeth. [[spoiler: What do you do when you have a broken ankle, no backup and no special powers, and nothing to defend yourself but a knife, while trapped miles underground and facing an enormous monster that hates you and everyone you love? Trick it into making a Chinese Handcuff and then trick it into trapping itself inside. Bravo, Annabeth.]]
* MarySue and MartyStu: Virtually all of the new main characters have been accused of this. Whether or not it's actually true is largely subjective, and dependent on how each reader defines the term. [[RuleOfCautiousEditingJudgement We]] ''[[RuleOfCautiousEditingJudgement really]]'' [[RuleOfCautiousEditingJudgement shouldn't go any deeper into the subject than that.]].
** If you think about it, it actually makes sense, this time there enemy are beings as powerful as Titan that can only be killed by Gods and Demigods working in tandem, which means that no amount of MarySue or MartyStu is going to cut it without any gods around (and given that most of them are incapacitiated do the Roman-Greek rift that sucks). And there major enemy is the EARTH, not some god who controls the Earth, like Hades. But the EARTH ITSELF, Gaia the literal personification who is literally the Grandmother of all monsters, who masterminded everything in HOO series(and she is ASLEEP while doing this), and is revealed by Aphrodite that if she is awake not only will the Gods can't beat them but she will "shake the western civilization off the earth". The heroes NEED to be MarySue in order to survive this type of threat.
* {{Moe}}: One could argue that Ella at least somewhat fits this trope.
* SugarWiki/MomentOfAwesome: [[Awesome/TheHeroesOfOlympus Has its own page.]]
* MoralEventHorizon: For many fans, Octavian seemed like a power-hungry jerk who would not do much harm. [[spoiler: Then he killed Gwen by stabbing her in the back -- and it was just luck that she managed to come back.]]
* OneSceneWonder: [[spoiler:Tartarus. Not the location, the primordial god himself. His description and abilities just ''scream'' EldritchAbomination, from having a swirling vortex for a face, to being able to suck souls, be they mortal, god, giant, or Titan, into said vortex face.]]
* PortmanteauCoupleName: Many. Percabeth, Percico, Reynabeth, Jeyna, Jasico, Jasper, Liper, Valgrace, Valdangelo, Frazel, Pipazel, [[spoiler: Caleo]], [[spoiler: Solangelo]]...
* RomanticPlotTumour: Jason and Piper's relationship in ''The Lost Hero'' can fall into this, as they spend a lot of time [[{{Wangst}} wangsting]] about their feelings for each other. As the readers have never met either of them before but ''know'' Piper's memories of Jason are fake it's tough to empathize with their feelings, [[note]] especially as lot of people assumed Jason/Reyna was the Roman equivalent of the iconic [[{{OneTruePairing}} Percy/Annabeth]] and jumped on that ship without even ''meeting'' Reyna. [[/note]] The romantic focus comes at the expense of their much-needed characterization and is probably one of the reasons why [[{{EnsembleDarkHorse}} Leo was so well-received]] - he's the only narrator not obsessing with a LoveInterest from the get-go.
* RescuedFromTheScrappyHeap:
** Piper's chapters were some of the harder-to-read parts of ''The Lost Hero'', for both her [[{{Wangst}} Wangsty]] inner monologues and being [[DamselScrappy an unfortunate subversion]] of the [[ActionGirl typical female treatment]] in the series. Fortunately, she [[TookALevelInBadass Takes Several Levels in Badass]] and becomes ''considerably'' more capable and self-assured as the series progresses, to the point where she defeats [[spoiler:Zethes, Cal, and freakin' ''Khione'']] with nothing but her wits, Katoptris, and an awesome application of Charmspeak. [[spoiler: She also gets her moment fighting the giant Mimas, trying to unleash the heatbeat of the chained god. Annabeth is freaking out as her plans fall apart, but Piper is the one that keeps her head cool and outsmarts the anti-Hephaestus. And let's not forget that her charmspeak became so powerful, she made freaking '''GAEA''' fall asleep for Leo to make the killing blow.]]
-->'''Piper:''' ''(to [[spoiler:Khione]])'' Still underestimating me. You really need to work on that. *Stab*
-->'''Piper:''' ''(to [[spoiler:Gaea]])'' [[spoiler: "One word. You want permission to close your eyes and forget your troubles. You—want—SLEEP." ]]

** On the flip side, Jason was maligned for ''not enough'' characterization beyond "Regain my memories, sort out my feelings for Piper, and save the day", being looked down upon as a rather bland StandardizedLeader. In ''The House of Hades'', he silenced many of his detractors when he underwent some ''serious'' CharacterDevelopment, became [[spoiler:Nico]]'s SecretKeeper, and [[spoiler:was forced to make a choice between the [[TwoRoadsBeforeYou Two Roads Before Him]].]]
* ShipsThatPassInTheNight: Leo/Reyna and Leo/Nico are surprisingly popular for pairings involving characters that don't have much overall interaction.
* SurprisinglyImprovedSequel: While not a terrible read ''The Lost Hero'' was a rather lackluster opening to the series, with the neglect of [[{{DemotedToExtra}} previous heroes]], [[{{Wangst}} Piper]] and [[{{FlatCharacter}} Jason's]] characterization and [[{{RomanticPlotTumour}} the focus on their relationship]] getting the most criticism. ''The Son of Neptune'' however saw the return of the beloved [[{{TheHero}} Percy]], brought back EnsembleDarkhorse Nico, introduced the BadAss Roman Camp and new character's Frank, Hazel and Reyna were much better-received.
* StrangledByTheRedString: Invoked in universe by Hera, as she implants poor Piper with fake memories of a relationship with Jason, even though they've never met in reality. Unfortunately this ended up up becoming an out-of-universe example too, as Piper and an amnesiac Jason are gushing about each other from the first chapter, without giving the readers a chance to get to know them - let alone how they work together. Then they get together off-page sometime before the ''Mark of Athena''. However subsequent books do develop their relationship better.
* TearJerker:
** Percy calls home for the first time in months and gets the answering machine.
** The later part of Hazel's childhood, particularly her death.
** Pretty much everything to do with Nico in ''The House of Hades''.
* ToughActToFollow: After the previous series ended in the incredibly high note of ''The Last Olympian'', some of this is to be expected.
* TheyWastedAPerfectlyGoodPlot: Embodied in the form of Aeolus, [[InsistentTerminology master]] of the wind. It's explicitly stated that minor gods (Boreas, etc.) are subservient to him. The Aeolian wind spirits mentioned in The Last Olympian are fast and powerful enough to prevent Titans from entering Olympus, at least by air. Everything appears to be setting up for a confrontation with what is arguably the most powerful god that doesn't have a seat on Olympus. When the heroes meet him ... he's a celestial TV weatherman. That's all he does. He tells the weather to a camera that goes to Olympus, and then prepares to do it again in less than a minute. What's more, he has been ''driven insane'' by this incredible responsibility that a literal ''[[PhysicalGod god]]'' [[SarcasmMode couldn't possibly handle, especially since gods can be in more than one place at the same time.]]
** The minor gods in general. Take Morpheus, god of dreams. A camper could pull {{Inception}}-style dream entries, or perhaps have supernatural powers of illusion. The possibilities are endless with minor gods like [[http://en.wikipedia.org/wiki/List_of_Greek_gods Deimos, god of fear, Hebe, goddess of youth, Lyssa, goddess of rage, Panacaea, goddess of healing, even Plutus, god of wealth]], but the only minor gods even given a named child are Hypnos, god of sleep, whose children are [[BlessedWithSuck narcoleptic]], and Iris, goddess of the rainbow, who doesn't even appear to give any powers to her son.
** What about the [[OurMermaidsAreDifferent mermaid camp?]] For everything in Camp Half Blood, there is an aquatic equivalent, with Merpeople being taught by Chiron's aquatic brother, quests, and various heroes, such as Triton and Bill. Perhaps they decided not to do this because AtlantisIsBoring, but it would probably be averted considering the amount of monsters and creatures that are shown to live underwater in the Percy Jackson series.
** Were you hoping for an UltimateShowdownOfUltimateDestiny between Percy and Jason, the two main leads? Well too bad, because you only get one chapter in ''The Mark of Athena'', they're both possessed, Piper keeps interfering with the fight so it's not fair, and it is never properly resolved anyway.
* UnpopularPopularCharacter: Nico. He creeps out most of the Seven (Hazel being the major exception; he still puts Jason on edge, but Jason is willing to cut him ''gallons'' of slack after gaining a better understanding of why he is the way he is) with his whole "son of Hades" thing and [[TroubledButCute generally brooding demeanor]]. This is not the case with the fandom, where he's well-loved and a main target of {{fangirl}}s.
* TheUntwist: The fact that Gaea is the new BigBad is pretty apparent before you're even halfway through the ''first story'' as long as you have a decent understanding of Greek Mythology. By the time you reach the point where it is "revealed" to the characters in the story, you kind of feel that Riordan was suffering from a pretty severe case of CannotSpitItOut.
* ValuesDissonance: An in-universe example from ''The Mark of Athena'': At Camp Half-Blood, being a child of Athena is nothing out of the ordinary. At Camp Jupiter, however, Minerva is revered as a virgin goddess, so when Annabeth goes there, the Romans are extremely shocked that a child of Athena/Minerva even exists -- and that she's leading the quest, since if a child of Minerva did exist, they wouldn't be heading up any quests, they'd be advisers at the most.
** Also in-universe, Hazel has some time-displacement related attitudes toward a lot of things. She gets more used to modern times as she goes, one of her friends noting in the last book that she openly and casually holds hands with her boyfriend in public when a few months ago it would have made her blush like mad and possibly pull away.
** Another in-universe example. Being from the past has some influence on Nico's [[spoiler: attitude towards his sexuality. He says later on that he would have accepted it in his own time, but having had a crush on the guy he blamed for his sister's death made him feel more guilty about his feelings than he might have otherwise. His angst about his sexuality seems to be only slightly influenced by the time he's from, but it is something he and Jason discuss in ''House of Hades.'']]
** Camp Jupiter has its own values and very strict laws, many of which involve capital punishment. In particular, in Blood of Olympus, Reyna has to explain to Nico exactly how serious it is that [[spoiler:she technically killed her father]], because [[spoiler:patricide]] is amongst the biggest and most horrible crimes in Roman society and automatically condemnable with CruelAndUnusualDeath.
* TheWoobie:
** Annabeth. She finally got together with Percy, he disappears four months later, and then she finds out he probably doesn't even remember her. He does, but still.
** Leo was tricked by Gaea into killing his own mother and then spent the next six or so years of his life trying to outrun the pain.
** Hazel [[spoiler: she was forced by her possessed mother to move to Alaska and raise Alcyoneus, where she made the decision to kill herself and her mother to delay Gaea's plan. Even before she was possessed, Queen Marie was emotionally abusive, blaming Hazel for being cursed. Plus, because of her curse she is indirectly responsible for a number of human deaths which she feels incredibly guilty for.]]
** Frank. His mother was killed fighting overseas, his grandmother died not long after and his whole life is bound to a stick.
** Ella. Her treatment at the hands of the other harpies and Phineas is [[TearJerker heartwrenching]].
** At this rate, Percy and Annabeth definitely qualify.
*** StoicWoobie: Reyna. Just... [[BrokenBird Reyna]].
** Nico. Freaking. di Angelo. Adding to his baggage from the first series, he escaped Tartarus, and then watched Percy [[spoiler:fall with Annabeth into Tartarus.]] Okay, that's pretty bad, but then it's revealed that [[spoiler:Nico is gay/bi and he had a crush on Percy! His reaction to having to admit it to Cupid in front of Jason is ''[[TearJerker heartbreaking]]'', made worse when Jason realizes that Nico was born in the 1930's, when that would have been completely unacceptable.]] At this rate, the fans are ''desperate'' for him to be happy.
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