Sim's Cerebus showed that "readers were interested in bound comic book collections, whether they were called phone books, comic book novels, albums or graphic novels". In 1984, Marvel shifted from trade paperbacks which were general collections to trade paperbacks which were notable recent runs such as the "Dark Phoenix Saga" and "The Power of Iron Man". Similarly, trade paperbacks were a "minor endeavor" for DC "until 1986's collection of The Dark Knight Returns". Brian Cronin, for CBR, highlighted that The Dark Knight Returns trade "was a true game-changer. The crux of the great Alan Moore/DC Comics feud is that Moore's deal with DC for Watchmen said that Moore and Dave Gibbons would get the rights to the characters once the book went out of print. At the time that Moore signed the deal, which was [before] the Dark Knight Returns was collected, the idea of a comic book staying in print was absurd. Well, by the time that Watchmen was finished, Dark Knight Returns was a sensation as a trade paperback and naturally, DC gave Watchmen the same treatment [...] and it's never been out of print since". The Dark Knight Returns, Watchmen, and Art Spiegelman's Maus (published as a collection in 1986 by Pantheon Books) "established a beachhead for 'graphic novels' in the book trade". In the 1990s, "trade paperbacks found their popularity boom". Comic book publishers began releasing trade paperbacks of collected story arcs directly after those stories' original periodical publication, because a new reader could purchase the trade paperbacks and access the entire series' stories to date. The Librarian's Guide to Graphic Novels for Children and Tweens by David S. Serchay explains: "At first it was the most popular stories that were being collected, but more and more comic book stories are now being put into trade, sometimes less than two months after the 'newest' issue is sold. And [...] not only recent material but a great deal of older material is finally being collected into trades". In 2015, Polygon highlighted that "though this was far less common a decade ago, pretty much every monthly comic out there right now is eventually collected into trade paperback or hardcover edition that prints several issues in one package". Additions and omissions "As with books, trades have an International Standard Book Number (ISBN) and a spine and come in a variety of sizes. In some cases, the pages of the