You've written [[{{Doorstopper}} a long book]]. [[LoadsAndLoadsOfCharacters Lots of characters]], many PlotThreads, and deep, complex CharacterDevelopment. Your publisher likes it, but unfortunately, you're not a very well-known writer, and readers aren't likely to pick up such a vast novel. Furthermore, limitations in the current printing and binding market make publication as a single volume uneconomical, especially if this is a debut novel; [[ if it goes over 424 pages in length]], it must be outsourced to a bindery that uses a more expensive technique, disproportionately increasing printing expenses.

The solution? Split the book into multiple volumes. The public will be less intimidated by the shorter length of the individual volumes, and thus more likely to buy them. There are also some practical reasons. For one, the smaller books are individually easier to hold and carry. Two, it places less physical stress on the bindings, so smaller books are less prone to fall apart while the consumer is still reading them. Three, it's easier to sell a cheap book than a costly one. There are also some economic issues in that the large page count has a higher per-volume production and transport cost, so it makes sense to divide that out to maintain a reasonable profit margin and/or price point.

If the book proves successful, it will probably be later released in a single-volume edition.

This happens with translated works, pithy phrases in the original language often require more words. In particular, English books translated into Romance languages get much wordier.

Note that this trope isn't intended for a series of books that tell a single story. This trope is for those stories submitted as single books, that were then split into multiples at the publisher's request.

A forerunner is the Victorian three-volume novel, a longer story is told and sold in three parts. In the 19th century, the business model was to use the first volume to get people interested in the second and third parts, and thus extract more money per story.

See also MovieMultipack, OneGameForThePriceOfTwo, TrilogyCreep, MultiVolumeWork. {{Omnibus}} is the opposite.


* The 620,000-plus-word [[WesternAnimation/MyLittlePonyFriendshipIsMagic MLP:FiM]]/''VideoGame/{{Fallout}}'' crossover ''FanFic/FalloutEquestria'' got broken into five volumes for its first printing. A second printing recombined these into two volumes.

* The Soviet-produced ''Film/{{War and Peace|1966}}'' was split into four parts when released between 1965 and 1967. The film as a whole ran a total seven-and-a-half hours. When released in the U.S., it was edited into a six-hour film in two parts.
* Unfortunately averted with ''Film/{{Cleopatra}}'' (1963). The director wanted to make a six-hour film that would be split into two volumes. 20th Century Fox wanted nothing to do with this and released it as a single four-hour production. The other two hours remain missing.
* ''Film/InTheNameOfTheKing'', the ''VideoGame/DungeonSiege'' adaptation by Creator/UweBoll, narrowly averted this. The original cut was over 200 minutes long and was planned to be split into two movies for theatrical release, but the editors couldn't find a spot in the middle where there was a good place to end the first installment. Instead, it was released as a single, heavily-cut two hour film in theaters and on DVD. The Blu-ray had an "Unrated Director's Cut" that restored a half hour of cut footage.
* The movie ''Che'' about the life of Guerilla leader Ernesto 'Che' Guevara had to be divided into two parts.
* ''Film/KillBill'' was originally going to be one movie, but was split into two volumes for release.
* The film adaptation of ''Film/HarryPotterAndTheDeathlyHallows'' was split into two parts, as the plot is very dense and the filmmakers decided that splitting it into two movies is a better choice than compressing the story. Also, before production of ''Film/HarryPotterAndTheGobletOfFire'', the producers considered splitting it into two movies, but decided against it. Consequentially, a few subplots had to be cut out for time.
* ''[[Literature/{{Twilight}} Breaking Dawn]]'' seems to have taken a page out of ''Literature/HarryPotter's'' book and is split into two parts.
* ''Literature/TheHungerGames'' novel ''Mockingjay'' has two parts as well.
* Richard Lester's ''Film/TheThreeMusketeers1973'' and ''The Four Musketeers'' were originally made as one film. It was only in post production that they decided to break it up into two parts. Many of the actors involved were somewhat upset, since they were only paid for ''one'' movie.
* ''Film/{{Superman}}'' and ''Film/SupermanII'' (from the same producers as ''The Three/Four Musketeers''), were written and filmed as one movie (only this time they were going to split it in two from the outset). Unfortunately, this time, the original director was fired after a significant portion of the second half was completed, so the two movies vary wildly in tone.
* The ''Franchise/{{Halloween}}'' franchise was originally supposed to be a series of otherwise unconnected stories with the only linking theme being that they take place on or near Halloween; it just so happened that the first story (about Michael Myers) took the first two films to tell. When ''Film/HalloweenIIISeasonOfTheWitch'' came out and it wasn't about Michael, fans were pissed and the producers reverted to just telling stories about the slasher.
* ''Film/TheAmazingSpiderMan2'' was so long that a number of scenes were cut and set to be used in ''The Amazing Spider-Man 3'', until Sony shelved the plans for ''3''.
* ''Film/TheHobbit'' trilogy was a 400-something page book, original scheduled for two films, and was then split into three. Each movie lasting more than two hours.
* The sequel to ''Film/BackToTheFuture'' developed into such a complex story that it was divided into two films, released six months apart. The [[Film/BackToTheFuturePartII second film]] even ended with a trailer for the [[Film/BackToTheFuturePartIII third]], a practice rarely seen since the demise of the cliffhanger serials of the early 20th century.
* Averted with the final film of 'The Maze Runner' trilogy, set to be released in 2018. [[ The director of all three films, Wes Ball, has confirmed this.]]
* The danger of this is highlighted withe the ''Film/{{Divergent}}'' franchise. The third novel, ''Allegiant'' was divided into two films, ''Allegiant'' and ''Ascendant''. The first part did so poorly that plans for the conclusion were scrapped with the idea of concluding it as a TV Movie.
* ''Film/JusticeLeague2017'' and ''Film/AvengersInfinityWar'' were both originally marketed as two-part movies, but ''both'' have since backed away from this, likely due to public burnout on the MovieMultipack trend (and the above failure of ''Allegiant''). Reportedly, both films will now have fairly distinct sequels, with the ''Infinity'' sequel getting its own title.

* ''Literature/TheLordOfTheRings'' was famously split into three volumes for publication, and in fact to this day is commonly (and erroneously) referred to as a trilogy. It is technically a single novel.
** This is further confused by the fact that each of the three "parts" -- ''The Fellowship of the Ring'', ''The Two Towers'', and ''The Return of the King'' -- is divided into two of what Tolkien called "books", making six "books" in total. This is using the meaning of "book" as a division of an epic.
* Similarly, the ''Literature/{{Illuminatus}}'' trilogy was originally pitched as one book, but split into three to have some hope of actually being read.
* Elizabeth Moon's ''Literature/TheDeedOfPaksenarrion'' also had to be split into three volumes.
* Creator/DavidWeber's first ''Literature/HellsGate'' novel was split into two books, and it seems likely the same will have to happen to his next ''Literature/HonorHarrington'' novel, ''A Rising Thunder''.
* Charlie Stross's first ''Literature/TheMerchantPrincesSeries'' novel was split into two books.
* ''Literature/{{Succession}}'' by Creator/ScottWesterfeld was split into two volumes, ''The Risen Empire'' and ''Killing of Worlds''. Confusingly, the book was published as a single volume in the UK, under the title ''The Risen Empire'' (704 pages in paperback).
* The UK edition of ''Literature/AStormOfSwords'' was split into two volumes, ''Steel and Snow'' and ''Blood and Gold'' (661 and 637 pages in paperback, including appendices). The French edition split it into ''four'' volumes - and, in fact, the French translations of all the ''Literature/ASongOfIceAndFire'' books were split into at least two volumes. And again in the UK with the A Dance With Dragons paperback, split into ''Dreams and Dust'' and ''After the Feast''. This happened in the American series as well, as ''A Feast for Crows'' came into being accidentally, originally intended to be ''A Dance with Dragons''. However, ''Dance'' was too large in whatever form it was in at the time, so George R.R. Martin split it into two books based on character [=POV=] groupings as opposed to chronology. Fans have since crafted reading lists that allow readers to follow the books' plots in chronological order just like the rest of the series.
* The first two books from ''Literature/TheWheelOfTime'' were split in half as part of a 'young adult special edition'. This doesn't seem to have done well, none of the other books were split. The German translation of the series has passed 31 books, corresponding to the first 11 books and prequel in the English version.
** The final three books - ''The Gathering Storm'', ''Towers Of Midnight'' and ''A Memory Of Light'' were originally intended to be one book ("Even if they have to invent a new method of bookbinding and sell it complete with its own library cart") but upon taking over the writing of the series after Jordan's death Creator/BrandonSanderson pretty much immediately decided to split it into thirds. Given the each of those three books are nearly a thousand pages, that was probably a good idea.
* ''Literature/TheNightsDawnTrilogy'' was split into six books for the American release.
* Creator/CliveBarker's ''Literature/{{Imajica}}'' was split into two volumes.
* ''Literature/TheTaleOfGenji'', due to its sheer length, is frequently divided into two volumes.
* Creator/TadWilliams has had a few:
** The Finnish translation of the ''Literature/MemorySorrowAndThorn'' trilogy was split into no less than twelve volumes. Even in English, the final volume was split in two for the paperback editions.
** ''Literature/{{Otherland}}'' has at the beginning of the first book an admission that it wouldn't be a series if it weren't for the fact that the author needs to keep writing new books at a constant pace so he'll keep receiving royalties.
** There's a note at the front of ''[[Literature/{{Shadowmarch}} Shadowrise]]'' remarking that the quartet was originally meant as a trilogy, and "one of these days I will learn to write a last volume that doesn't need its own zip code."
* Creator/CJCherryh:
** In the ''[[Literature/ChanurNovels Chanur]]'' series, where the middle three of the five novels were one novel split into three to satisfy publishing constraints; they form one story arc, with no mini-resolution at the end of each. Although they've been published together in an omnibus since, but have never been printed as Cherryh really intended, as one novel.
** Also, ''Literature/{{Cyteen}}'' was published in mass-market paperback form as three novels, although it was released in hardback and "trade paperback" form as a single work.
* Proust's ''Literature/InSearchOfLostTime'' was originally published in seven volumes, due to its length. Modern versions are usually in 2, 6 or 7-volume sets.
* Creator/LoisMcMasterBujold originally submitted the first two books of ''Literature/TheSharingKnife'' as a single book.
* {{Inverted}} with ''Literature/JonathanStrangeAndMrNorrell'', which was intended to be in the style of the Victorian three-volume novel, but ended up as one giant-ass book. (It did, however, end up published as three volumes in Poland.)
* In a weird case, ''Literature/TheBelgariad'' was originally intended to be a trilogy, with the three volumes named ''Garion'', ''Ce'Nedra'', and ''Torak'' after three key characters in the story. The author was asked to split the story into five parts instead of three, resulting in the series as we know it. This is noticeable starting in the second book:
** The climax of the second section (of three) in the second book is the climax of the main character's development up to that point.
** The final section of the second book is a mostly self-contained episode in the story, but it sets up the quest that takes all of the third book (which ends on a {{Cliffhanger}}) and that isn't properly resolved until early in the fourth.
** The second half of the fourth book and all of the fifth book function together as a single unit, with most of the main character's subplot in the fourth book and almost all of the SupportingLeader's subplot in the fifth book.
* The Dutch translation of the later "stand alone" books of Literature/TheBelgariad (''Belgarath the Sorceror'' and ''Polgara the Sorceress'') and of Literature/TheRedemptionOfAlthalus were all published as two books.
** Same for the French translation of the former.
* Creator/CliveBarker's ''Books of Blood''.
* ''Literature/TheKingkillerChronicles'': Rothfuss wrote the whole story over 14 years, submitted it, then publisher says make it a trilogy, so he has to rewrite it yet again.
* ''Literature/RomanceOfTheThreeKingdoms'' is often divided for publication, as is ''Literature/JourneyToTheWest'' and other classical Chinese novels.
* ''Literature/AshASecretHistory'' by Creator/MaryGentle was split into four parts for US publication.
* Three-volume novels? ''Literature/JaneEyre'' comes to mind, though it's now typically published as an omnibus.
* The second and third of Creator/GarthNix's Literature/OldKingdom books are basically one story, but apparently after finishing ''Lirael'' he realized that this was getting [[{{Doorstopper}} way, way too long]] for a single young-adult-aimed fantasy novel and split it in half.
* The first book of Literature/TheRiftwarCycle by Raymond E. Feist, ''Magician'', is usually published in two parts, called ''Magician: Apprentice'' and ''Magician: Master''.
** This may vary by region. In Australia it is more common to find it published as a single volume and only imported versions split into two parts.
* Back in the day, this happened with some non-fiction books as well. There are dual volume versions of John Toland's ''The Rising Sun'' and William Shirer's ''Rise and Fall of the Third Reich'', and to this day, some publishers still release Solzenitsyn's ''Literature/TheGulagArchipelago'' in three volumes.
* The German translation of ''[[Literature/HandOfThrawn Vision of the Future]]'' was split into two volumes.
* Another translation split. The Japanese versions of the ''Literature/HonorHarrington'' books are split in two starting with the third or fourth book. Possibly more with [[{{Doorstopper}} the later volumes]]
* Literature/TheBible's Old Testament books of 1 Samuel, 2 Samuel, 1 Kings, and 2 Kings were originally one book. So were 1 Chronicles, 2 Chronicles, and Ezra (the dividing line between the end of 2 Chronicles and the beginning of Ezra is in the ''middle of a sentence''). These were split in the Septuagint, with the Vulgate following the same convention, because the scrolls used by those "publishers" couldn't fit the text of the whole book. Making this ExecutiveMeddling that's OlderThanFeudalism.
* The second volume of the ''Literature/WarsOfLightAndShadow'' series, ''Ships of Merior'' was such a {{Doorstopper}} that it couldn't be published in paperback form as one book. So the paperback version is split into two volumes, entitled ''Ships of Merior'' and ''Warhost of Vastmark''.
* This happened to Creator/IsaacAsimov several times, most notably with his autobiography. He hated this more than other authors, because he would then have to decide whether to count it as one item or two on his list of published books, with good arguments for either choice.
* Not quite an example, but related: some editions of Haruki Murakami's ''Literature/NorwegianWood'' split the novel in two very small volumes, one red and one green (sometimes inside a gold-coloured case, as per [[ here]]). As the novel is not particularly long (and in at least one case the split causes a mid-chapter break), this was presumably done for strictly aesthetic reasons.
* Creator/HarlanEllison's anthology ''Literature/AgainDangerousVisions'' was published in two volumes in UK hardcover, but confusingly split into ''three'' volumes in paperback.
* The first story in Alan Dean Foster's ''Literature/{{Spellsinger}}'' series was split into ''Spellsinger'' and ''The Hour of the Gate''.
* Creator/SergeyLukyanenko's ''Literature/SeekersOfTheSky'' was split into ''Cold Shores'' and ''Morning Nears'' with the second novel picking up immediately after the first (after a day-long TimeSkip).
** While this may also seem to be the case with his ''Rough Draft'' and ''Final Draft'' novels, as ''Final Draft'' picks up a few hours after the ending of ''Rough Draft'', it took Lukyanenko 2 years to write the sequel.
* This has happened twice to novels by Creator/RobinHobb, much to many readers' confusion.
** The first two books of what is now known as the ''[[Literature/RealmOfTheElderlings Rain Wilds Chronicles]]'' were written as a single book that was split into two.
** Hobb then set out to write a sequel which was also split, resulting in books three and four of the series.
** The French version of Hobb's ''Literature/{{Farseer}}'' trilogy had its second book split in two, and the third one split in three.
* Gene Wolfe's ''Literature/BookOfTheNewSun'' was written as a single novel and published as a series of four. Most later editions of it divide it into two books.
* Supposedly the "Graystripe's Adventure" manga trilogy of the ''Literature/WarriorCats'' series was originally meant to be a single volume as long as a normal manga. They decide that it should be released on the same day as the first book in a new series, but the illustrator wasn't done with it, so they decided to split it into three shorter volumes. Every manga afterward has followed suit.
* The ''Literature/LegacyOfTheAldenata'' books ''When the Devil Dances'' and ''Hell's Faire'' were originally to be published as one volume. However, the [[TheWarOnTerror September 11, 2001]] attacks left Creator/JohnRingo unable to work on the book for a time, running up against the scheduled publishing date. The work was split into two books to keep it from being extremely late (instead of only somewhat late), as explained in [[WordOfGod the afterword]] of ''Hell's Faire''.
* When Creator/DouglasAdams was adapting his radio play ''Radio/TheHitchhikersGuideToTheGalaxy'' into [[Literature/TheHitchhikersGuideToTheGalaxy1 book form]], he took so long that (as he reported it) his publisher rang him up and told him to finish the page he was on and send the whole thing over, they'd release the rest as ''Literature/TheRestaurantAtTheEndOfTheUniverse''.
* Creator/PeterWatts's Literature/RiftersTrilogy novel ''ßehemoth'' was split by Tor Publishing into two books: ''ßehemoth: ß-Max'' and ''ßehemoth: Seppuku''. This did not go over well with Watts.
* Neal Stephenson considered his Literature/TheBaroqueCycle to be either one '''very''' long book or series in eight volumes. The series was eventually published as a trilogy of three books, with each book contained two or three of the volumes in the series. Stephenson also took advantage of this set up in the second volume by presenting two volumes in one jumble, alternating between chapters of the first volume and second volume so that the two books come together to tell a single coherent story.
* Creator/TamoraPierce's first book, ''Literature/SongOfTheLioness'', was originally intended as one book for the adult market. She had to cut and rewrite it into four parts to market it as a young adult title.
* Creator/CordwainerSmith's ''Norstrilia'' was originally split into two volumes, ''The Planet Buyer'' and ''The Underpeople''. It took the better part of another decade for the complete novel to be published. To make the novel fit better into a 2-volume format Smith added some new material to the end of one book and the beginning of the next. The additional scenes are not necessary to the plot, but may be of interest to Smith completists.
* ''Artamene'', a 1600s novel published in ''ten'' volumes, spanning a total of 2.1 million words.
* Books three and four of the ''Literature/{{Rihannsu}}'' series were originally meant to be one volume, but ExecutiveMeddling forced ''Literature/{{Swordhunt}}'' to be split in two, creating ''Literature/HonorBlade'', with the chapter numbers starting at six. The ''Rihannsu: The Bloodwing Voyages'' {{omnibus}} merges them back together.
* The paperback reprint of Creator/StephenKing's book ''Literature/UnderTheDome'' is split into two books, each over ''600'' pages on their own.
* ''Literature/LesMiserables'' by Creator/VictorHugo is over 1900 pages in the original French, and to this day is usually published as two separate volumes. English translations usually come in around 1500 pages (more with appendices); some of these are published as two volumes as well.
* Creator/LewisCarroll's ''Literature/SylvieAndBruno'' was written as a single novel, but due to its length, his publisher suggested it be released as two volumes. Thus it was separated into ''Sylvie and Bruno'' and ''Sylvie and Bruno Concluded'' published four years apart.
* ''Literature/LeviathanWakes'' has been published in Poland as two books.
* In the Literature/DoctorWhoNovelisations, the very long TV story "[[Recap/DoctorWhoS3E4TheDaleksMasterPlan The Daleks' Master Plan]]" was split into two books. "The Trial of a Time Lord" was split into four books, but it had been originally produced as four separate TV stories and comes across more as a season with an unusually strong StoryArc than as a single story.

* Music/SimpleMinds recorded many songs for Sons And Fascination, and liked so many that they couldn't fit them all onto one album (optimum space for a vinyl LP is about 22 minutes per side). They initially were going to put out Sons And Fascination as a double album, but decided that might make people think they were a pretentious prog rock group rather than the new wave band they wanted to be. Instead, they released the second half as a separate album called Sister Feelings Call. This was originally shrinkwrapped with Sons And Fascination, and later sold as a budget release. Both albums are available on one CD and are now considered by the band to be one album again simply titled Sons And Fascination/Sister Feelings Call.

[[folder:Video Games]]
* The episodic release model tries to be like this, but in practice, it rarely takes off.
* The [[InteractiveFiction text adventure game]] ''Dungeon'', originally developed for the PDP-10, was adapted into the ''VideoGame/{{Zork}}'' games for microcomputers, due to memory / disk size limitations. ''Zork 1'' and ''Zork 2'' are the two halves of the original ''Dungeon,'' with a few details added to each to round them out. ''Zork 3'' (other than one puzzle) was developed ''de novo'' by Infocom.
* ''[[VideoGame/Sonic3AndKnuckles Sonic 3 & Knuckles]]''. It had to be split into two cartridges: [[CaptainObvious Sonic 3, and Sonic & Knuckles.]] However, thanks to the "lock-on" technology, which allowed users to insert their ''Sonic 3'' cartridges onto ''Sonic & Knuckles'', this became [[TropesAreNotBad kind of a good thing]], as otherwise Knuckles probably wouldn't have become playable, much less in ''VideoGame/SonicTheHedgehog2''.
* ''VideoGame/GoldenSun'' and its direct sequel were conceptualized as one game. When the game shifted from the N64 to the GBA, it had to be split due to space limits. [[TropesAreNotBad However, one could argue that the narrative ended up ''better'' as a result:]] [[spoiler: The main character of the second game is an antagonist from the first, and the game explores his much more complex motivations.]]
* In Japan, the PCEngine port of ''VideoGame/RType'' was released in two separately-published [=HuCards=] titled ''R-Type I'' and ''R-Type II''. ''R-Type I'' contains the first four stages and after completing them, the player is given a password that can be used in ''R-Type II'' to carry over lives, score and power-ups from the first game. Likewise, finishing ''R-Type II'' gives a password that starts the second loop in ''R-Type I''. In America, Hudson managed to combine both games into one [=TurboChip=] and the game was later re-released in Japan as a CD-ROM titled ''R-Type Complete''.
* The UsefulNotes/{{Atari 2600}} port of ''VideoGame/{{Miner 2049er}}'' was released in two parts due to system limitations, but even both put together had only 6 out of the original 10 levels.
* The first two installments in ''Creator/{{Falcom}}'s ''Franchise/{{Ys}}'' series, ''Ys I: Vanished Omens'' and ''Ys II: Ancient Ys Vanished'', were originally envisioned as one game, which is why most remakes, starting with the UsefulNotes/{{TurboGrafx CD}} version feature both games in one package.
* Falcom's ''VideoGame/TheLegendOfHeroesTrailsInTheSky'' also needed to be divided. The game that would be known as Trails in the Sky First Chapter was released at a good stopping point before the story begins in earnest. The second game starts immediately after the first ends as a direct continuation. Considering the First Chapter clocks in at above 400000 words, and the second at more than 700000, you can see why the plan to publish it as one large game needed to be scrapped with its [[DoorStopper sheer volume of text]], to say nothing of the stint of DevelopmentHell for the translation team at ''Creator/XSeedGames'' to localize it all. When Second Chapter came out, the PSP port required two UMD drives to play, making it one of the largest games on the handheld. Thankfully The Third written after the games were published is a still long, but more managable 250000 words or so, acting as an extended epilogue.
* History repeated itself with ''VideoGame/TheLegendOfHeroesTrailsOfColdSteel 2'', which was so large that it capped the size limitation of the ''Vita'' where it was natively published, requiring Falcom to create a third game to put in the remaining material.
* The ''VideoGame/{{Shenmue}}'' series was supposed to be released in serialized installments that would have spanned 16 chapters across at least three or four games for the UsefulNotes/{{Dreamcast}}. But since the first two games failed to recoup their expensive development budget (even after ''Shenmue II'' was ported to the Xbox), the third game in the series has languished in {{development hell}} since Sega almost fell into bankruptcy as a result of the series' commercial failure (forcing the company to quit the hardware race and become a third-party developer for their former competition).
* ''[[VideoGame/MetalGearSolidVThePhantomPain Metal Gear Solid V: Ground Zeroes]]'' was originally intended to be a prologue portion of ''[[VideoGame/MetalGearSolidVThePhantomPain Metal Gear Solid V: The Phantom Pain]]'', but was repurposed as a stand-alone game with several additional missions set in the same location as an appetizer due to the prolonged development of the main game. As an incentive to get people to buy both games, completing ''Ground Zeroes'' unlocks additional content for ''Phantom Pain''. Eventually both games were released as a bundle titled ''Metal Gear Solid V: The Definite Edition''.
* ''Episodes I'' & ''II'' of ''VideoGame/{{Xenosaga}}'' were originally intended to be one game. About half the original trailer for ''Episode I'' is comprised of scenes that don't occur until ''Episode II''. Monolith later published a version for the UsefulNotes/NintendoDS which had the plot of both games forged into a single cohesive narrative aptly titled ''Episode I&II''. They never stated [[SchrodingersGun which version was canon]] vis-a-vis the rest of the series, though.

[[folder:Web Original]]
* Creator/UrsulaVernon of ''Webcomic/{{Digger}}'' fame had a WebSerialNovel called "Black Dogs" which is making the jump to print in two parts - as of mid-2009, only Part One is out.

* Sets of Architectural and Engineering design drawings require special bindings and storage techniques that publishers don't use. A single 36"x48" design drawing printed out on paper weighs more than a 72 page (36 sheet) trade paperback. They aren't bound with glue. They are bound with staples or screws. Hand drawn antique mylar, vellum, sepia, and/or linen originals are much heavier and often stored unbound in drawers so that they won't distort.
* This is a common practice in Japanese publishing in general. Books with a high page count will often be released as two or more smaller volumes of no more than 200 pages or so. There are a few reasons for this, but one is because this is thought of as more practical; compared to a full-length book, a couple of slim softcovers are more portable (the better to bring on the long train commute to and from work) and take up less shelf space in cramped apartments.