* AlternateAesopInterpretation: In ''Black Water'', the world Eelong features a world where the cat people Klees keep the humans, Gars, as pets and slaves. The message is an anti-racist and [[SlaveryIsASpecialKindOfEvil anti-slavery message]], but can be read as being pro-animal rights, because you might not like it if your roles were reversed.
* AlternateCharacterInterpretation:
** Is Press Tilton the good uncle to Bobby who wants to make sure that he is prepared for the hardships of the future, or a sociopath who manipulated him into becoming his unwitting pawn to further his own goals despite the risks to his nephew? [[spoiler: Keep in mind that Press is not his actual uncle, nor a human. And neither was Bobby]].
** Press Tilton mentions in book 10 that Saint Dane was once a WellIntentionedExtremist who wanted to do good but later became a monster with a God complex obsessed with pleasing only himself. Is this actually the case, or was Press's perspective colored by memories of his old friend and preventing him from seeing that Saint Dane was always the monster that he is in the present?
* {{Anvilicious}}: The books are not always particularly subtle about their Aesops. The worst example is probably ''The Quillan Games'', which at one point has Saint Dane gloat for several pages about how he didn't ruin this particular territory, unrestrained capitalism did it for him.
* AssPull:
** Suffice to say that pretty much ''no one'' predicted what the actual answers to the series' [[DrivingQuestion driving mysteries]] (Where do the travelers come from? How does evidence related to their lives disappear? Where is Saint Dane from and how is he so much more powerful than the other travelers?) would be, mainly because most of those answers revolve around the sudden introduction of [[spoiler:Solara]] in the last book. The fact that years of theorization ended up being AllForNothing because hugely important puzzle pieces were missing without any sort of {{Foreshadowing}}[[note]]The only thing ''close'' to a clue given was Saint Dane's extremely cryptic [[TheUnreveal "reveal"]] that the Travelers were "not real", which Bobby outright dismissed as Saint Dane trying to [[MindScrew screw with him]][[/note]] did ''not'' go over well with the fans, which is one of the major reasons Book 10 was so poorly received.
** The Travelers being [[spoiler:bodiless spirits from Solara]] is similarly an AssPull, as they were more than capable of [[spoiler:being maimed or even dying before,]] with Gunny [[spoiler:losing a hand,]] Kasha [[spoiler:being crushed to death,]] and [[DroppedABridgeOnHim Aja]] [[spoiler:being murdered offscreen.]] While Loor was [[spoiler:resurrected inexplicably]] and both her and Bobby were unsettled by the experience, it had been heavily implied that Loor was [[spoiler:sent back by the souls of the other Travelers [[ItIsNotYourTime because she was still needed]]]] rather than because of some inherent ability of the Travelers to [[spoiler:dodge death]] as long as they knew they could. Hell, when Saint Dane said [[spoiler:the Travelers weren't "real",]] Bobby immediately dismissed it as [[ConsummateLiar Saint Dane]] [[MindScrew trolling him.]]
** TheReveal that [[spoiler:Alexander Naymeer]] was meant to be Bobby's mentor rather than Press. [[VoodooShark Not only does this make no sense,]] as [[spoiler:Naymeer died of tuberculosis as a child]] long before Bobby was even ''born'' before [[TheDragon Nevva Winter]] [[spoiler:altered the timeline so he'd survive,]] Nevva had to take Mark's acolyte ring to give him his powers, something the Travelers have never been dependent on for any power besides communicating with each other across Halla before now.
** The ending immediately manages to AssPull and contradict what was said in the last five minutes. [[spoiler:Press explains that Solara is so heavily weakened from the battle with Saint Dane that everyone displaced to a different Territory will have to stay there permanently, and that the Travelers must return to Solara. Bobby laments not having been able to live a normal life, when suddenly it seems like the ResetButton was pushed and the series' events never happened, with Bobby marrying Courtney and living a fully mundane life on Second Earth. When he's dying of old age after living said long life, Press appears (not having aged a day) and gives Bobby his journals. End book.]] This ending was so jarring many readers believe [[DelusionConclusion it took place by having Bobby plugged into Lifelight to live out his perfect fantasy life.]]
* AudienceAlienatingEnding: Starting with Book 8, the series is seen as declining in quality, ending with a very poorly received Book 10 due to several reasons (including VillainDecay, a ResetButton ending, breaking up the [[FanPreferredCouple Fan Preferred Couples]], dropping a bridge on [[BreakoutCharacter Mark]], and some [[AssPull rather out-of-nowhere]] [[TheReveal reveals]] about the MythArc) that make it hard to recommend the series to newcomers.
* BadassDecay: Saint Dane is nowhere near as scary when he's holding all of the cards, possibly because a lot of his creepiness comes from good ol' fashioned ParanoiaFuel - Saint Dane can be ''anyone'', anywhere, at any time. Once he's won, he really has no reason to hide, which means the Travelers know where he is at all times and much of his fear factor evaporates.
* CompleteMonster: The shapeshifter, [[BigBad Saint Dane]], manipulates [[TheChessmaster catastrophes across parallel universes]], called "territories", ensuring they result in the worst possible outcome. [[ManipulativeBastard Manipulating]] the oppressed people of a territory, Saint Dane causes a catastrophic war to destroy their planet; on another planet, creates a poison to kill the plants in the hopes of creating mass famine; on Earth, gives nukes to the Nazis to help them win UsefulNotes/WorldWarII; on a jungle planet, tries to use his poison again in the hopes the natives will hunt each other to extinction; on a desert planet, inflames tensions, trying to lead to one tribe being wiped out; and on yet another planet, crushes a rebellion against tyranny, ensuring the people would continue to suffer in the dystopia. Using the Cult of Ravinia to conquer various worlds, Saint Dane has those he deems too weak killed or banished, while trying to [[GodhoodSeeker become a God]].
* DelusionConclusion: Many people believe [[spoiler:the sudden contradictory ending]] is really just [[spoiler:Bobby experiencing the perfect, normal life he really wanted at the end of the series in Lifelight.]]
* DracoInLeatherPants: Saint Dane. Looking like [[VideoGame/FinalFantasyVII Sephiroth]] in the graphic novels certainly helps matters.
* EpilepticTrees:
** A somewhat common speculation on forums what was all the territories would turn out to be Earth. Despite the fact that Eelong is in a star cluster and Denduron has three suns.
** Many people believed Bobby would become Saint Dane far in the future, with several theories arising as to how Saint Dane's promise was somehow tied in with saving someone Bobby held dear and how that tied in with sending territories on the 'wrong' path. This was jossed in ''The Soldiers of Halla''.
** Another popular theory is that [[spoiler:[[DelusionConclusion the end takes place in Lifelight, and nothing's really been reset,]] though this makes the BittersweetEnding into an EsotericHappyEnding when FridgeHorror kicks in.]]
* EvilIsCool: Saint Dane, who's a ManipulativeBastard and one of the coolest characters in the books by far.
* FanDislikedExplanation: This is the usual reason people hated the last book. The existence of [[spoiler:Solara]] came out of nowhere and some important questions (such as whom Saint Dane made his promise to) were never answered. Even worse, this explanation [[VoodooShark raises further questions,]] such as whether [[spoiler:Veelox]] was always doomed to fail given the existence of [[spoiler:Ibara]] was contingent on its fall.
* FanPreferredCouple: Mark/Courtney and Bobby/Loor were both by far more popular than the canon ending pairing of Bobby/Courtney due to many fans believing having Bobby and Courtney together at the end undid a lot of both characters' character development.
* GrowingTheBeard: Some people think that the later books are an improvement over the first ones. More specifically, some think the series starts off rocky with the first two books, but gets really good starting from the third book, with the strength continuing to grow through at least the seventh.
* HarsherInHindsight: As Saint Dane explains in ''The Quillan Games'', the MegaCorp of Blok started out as an ordinary convenience store, but gradually managed to gain a stranglehold on the market by selling its goods at a much lower price than other businesses could afford to offer. Despite how cheap and bland Blok's mass-produced goods were, the convenience and low prices made them irresistible to consumers, which led to all of Blok's competitors going out of business due to being unable to keep up. Now with an effective monopoly, Blok gradually began expanding into other areas, including entertainment and technology, applying the same formula to crush competition in these sectors. Flash forward several years after the book's publication and the whole backstory feels uncannily similar to the growth of Amazon, a company which has similarly been accused of achieving near-monopoly status among online retailers by vastly underselling its competition and has expanded into areas such as technological innovation and even producing its own television content.
* LoveToHate: Saint Dane is the biggest monster in the entire series bar none but his intelligent dialogue, personal rivalry with Bobby and status as a ManipulativeBastard makes him one of the most popular characters in the series by far and an interesting villain in general.
* MisaimedFandom: Those who love Saint Dane [[DracoInLeatherPants despite his monstrous villainy]] rather than [[ManipulativeBastard because of it.]] It's safe to say that a lot of fans wanted him to win at the end of the series. Also, [[spoiler:some love Nevva Winter even though she's almost as much of a monster as he is (though at least she shows hints of a redemption arc shortly before her death).]]
* MoralEventHorizon:
** Saint Dane [[spoiler:seducing Courtney and becoming her LivingEmotionalCrutch, only to use the opportunity to run her over and leave her for dead in a ditch]].
** [[spoiler:Naymeer]] crosses the MoralEventHorizon line by orchestrating the deaths of thousands of people at once in a baseball stadium under the pretense of trying to win them over.
* NeverLiveItDown: D. J. [=MacHale=] mistakenly thought hentai was another word for generic anime, leading early prints of ''The Merchant of Death'' to refer to "cutesy hentai" posters on Mark's walls in his room. [[{{Bowdlerise}} While the line was changed in later reprints of the book,]] this didn't stop the fandom from jokingly characterizing Mark as a CovertPervert into [[AllAnimeIsNaughtyTentacles tentacle porn.]]
* ParanoiaFuel: Saint Dane could be ANYONE.
* PlatonicWritingRomanticReading: Mark and Courtney spend the entirety of the series getting close to one each other. Mark is the one to save Courtney from [[spoiler:one of Saint Dane's attacks]] and he spends time in the hospital by her side. Courtney's boyfriend, Bobby, [[spoiler:ends up breaking up with Courtney since he fell in love with Loor, a sentiment that Courtney accepts as she feels she has grown apart from Bobby in the many years he's been gone]]. In book 8, Mark and Courtney share an AnguishedDeclarationOfLove at gunpoint that made fans think the two had become an OfficialCouple... Except Creator/DJMacHale clearly hadn't meant it that way, since the whole thing was entirely ignored in book 9 and the series ends with [[spoiler:Bobby and Courtney getting back together and growing old together.]]
* {{Sequelitis}}: Many consider the last three books to suffer from a gradual decline in quality compared to the ones before, although Book 10 is where things ''really'' get contentious.
* ShipMates: Bobby/Loor and Mark/Courtney, or Bobby/Loor and Courtney/Spader, depending on your preferences.
* {{Squick}}: Saint Dane [[spoiler: seduced Courtney while disguised as a human teen]] to further his plans. Ick.
* TheyWastedAPerfectlyGoodPlot:
** Saint Dane's promise from book 6 is hinted to be an important clue towards the story's MythArc and the key to explaining Saint Dane's motivations for tipping the Territories towards destruction [[spoiler:and then merging them together]]. This plot point ends up never being brought up after book 7, the MythArc ends up being resolved via an AssPull, and Saint Dane is never given any motivations besides simply wanting to recreate the universe ForTheEvulz.
** Part of what made ''The Soldiers of Halla'' so disliked was that the ending to ''Raven Rise'' set up all the Travelers finally coming together to destroy Saint Dane for good. Come ''The Soldiers of Halla'', most of the Travelers are PutOnABus doing absolutely nothing of note offscreen while Bobby runs around occasionally speaking to one or two of them only for them to promptly disappear again once they're done interacting with him.
** Press says [[spoiler:that to avert any more damage to Halla, anyone displaced from their Territories must stay where they've been brought to, including Courtney and Mark in the ruins of Third Earth. Instead of exploring the consequences of this and people's efforts to rebuild and integrate in their new worlds, Bobby complains that [[ItsAllAboutMe he doesn't get to go back to his normal life]] and we're treated to a MindScrew ending contradicting everything that Press just said about Solaran spirits not being part of their worlds and the damage to Halla being irreversible]].
** Third Earth never gets a turning point, instead becoming a WretchedHive as part of Saint Dane manipulating Second Earth's timeline.
* TooCoolToLive: Vo Spader, the BreakoutCharacter SurferDude Traveler from Cloral, would clearly have overshadowed Bobby if he were kept in the story for any long periods of time, hence his multiple [[PutOnABus bus trips]].
* UnintentionallyUnsympathetic: Nevva Winter's [[spoiler:death is meant to be a tragic redemption moment after learning she was a HalfHumanHybrid who never felt like she belonged anywhere.]] However, most fans thought she'd crossed the MoralEventHorizon after [[spoiler:threatening to murder Mark's parents so he'd give her his Acolyte ring and founding the Cult of Ravinia,]] finding her FreudianExcuse to be too little too late and treating her death as a KarmicDeath, especially since her death was a TooDumbToLive moment after she [[spoiler:admitted to betraying Saint Dane by saving some dissidents under his nose because she had doubts about his plan.]]
* VanillaProtagonist: Bobby is a normal jock teenager suddenly whisked away on a grand adventure (initially without his consent). His ultimate goal is to be able to go home to Second Earth and live a normal life. He contrasts the colorful and often more experienced Travelers around him, such as SurferDude Vo Spader or badass AmazonianBeauty Loor. In-universe this is deliberate, [[spoiler:as he is a Solaran spirit meant to become as typical of a resident of Earth as possible to better serve his Territory's interests]].
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