In-Game Novel

Many video games have backstories, often told via tidbits of information that the player can only read a little of at a time. This is the Pamphlet Shelf.

Rarely, however, some games go so far as to actually have a full, readable story, from beginning to end, within the game itself. Some of these stories are almost long enough to be real published novels! This is the In-Game Novel. Naturally, because writing an actual full-length novel is time consuming and possibly costly depending on how much the author is paid, these tend to be shorter than the average published novel, but still very long by video game standards.

Compare In-Game TV. Contrast Pamphlet Shelf.

Examples of In-Game Novel include:

The Elder Scrolls series is known for having a robust background in books and scrolls. These books tend to range wildly in size from 2 pages to over 30 pages, and range from personal journals to ballads to historical texts to short stories, to outright novels. Some of them are The Real Barenziah, King Edward, The Last Year of the First Era, and The 36 lessons of Vivec.
Deus Ex contains a handful of chapters of a book that you can read. The protagonist discovers them as he goes along, and the book happens to uncannily mirror his current situation. One, "The Man Who Was Thursday", is a real novel; the other, "Jacob's Shadow", is not.
- The Sequel Deus Ex Invisible War included several chapters of "Jacob's War", which was apparently a sequel to "Jacob's Shadow".
Super Mario Galaxy contains a full illustrated children's book in the game. The book is substantial by video game standards, contains painted illustrations on each page, and could easily pass for an actual children's book. It details the backstory behind Rosalina.
Silent Hill 3 has a "crappy fairy tale", as Heather put it, that can be read. It's divided into a beginning, middle and end that can be read out of order, yielding different thoughts from Heather based on what order you read it in. You're only required to read the ending to leave the office building.
Paper Mario: The Thousand-Year Door had the Super Luigi books, which formed quite a long story by video game standards when you put them all together.
- Made even more funny by the fact that Luigi tells you the same story... but it is noticeably different from the book version. You get to decide for yourself whether the book story was altered when published or if Luigi's just trying to make the tale more interesting on his own.
One of the books in The Riddle of the Sphinx is the entirety of the third book of the Old Testament.
The Neverhood has The Hall of Records, a 30-something-screen-long hall along the length of which almost the game's entire backstory is written. Yes, seriously. And there's a Plot Coupon with more backstory that requires traversing the entire hall to pick up.
World of Warcraft has books scattered all over the game world containing pieces of the lore of the game. The expansion dropped this habit for the most part, as well as contradicting a lot of said lore in a massive Retcon to pave the way for the two new playable races.
Ultima Online not only had books that were readable (though none as long as a full novel), you could also buy blank books and write your own story, for the public to read. Some of these could be quite epic in length.
Wild ARMs 3 and Alter Code F have chapters of a book that you can collect and read. The first being a Wild ARMs 2 Fanfic with Marivel and Anastasia, the second being some other story entirely.
Completing a mission in Outpost 2 unlocks another chapter of the game's pair of novellas, uncovering a tale of survival for your chosen colony of Plymouth or Eden. The novels tell much the same story, but from the perspectives of two Elders (the original colonists from Earth); one of whom stayed with Eden, and the other left to found Plymouth. The only difference, in the end, is who comes out on top. Also, three quarters of the structures have short stories associated with them, too, such as a father showing his son the newly built light towers - and receiving a complaint about not being able to see the stars now, to combat stories around manually piloting the robotic vehicles. More than a few of them tie directly into the novellas, and all take place in the same continuity. In all cases, the quality of the writing is remarkably high, for being written to go with a relatively old RTS game.
Metal Gear Solid 2 includes a humorous short story tying into the events of the first game, a book review on a novel written by one of the support characters in the first game on its events from her POV and the book itself as extras.
As books are a major theme of the Myst series, naturally there are several readable books in the games. Most of them give you backstory to the various worlds and characters, also occasionally giving puzzle clues.
Odd non-game example: The book version of Penn & Tellers Cruel Tricks for Dear Friends contained fake compilation of Sci-fi short stories that was used for only a single trick. However, aside from the one caveat of the trick, the stories were all fleshed out and some were written quite well.
Myst: Uru: typically, any book or note you find in a Myst game reveals agendas of the little-seen other chracters in the game, expose secrets and clues, or describe the different Ages of the game. Well-written stuff, actually, and very informative. In Uru, however, there is a rotunda of many books devoted to telling stories about the former rulers of the D`ni. There is no puzzle.
- As a bonus, part of the walkthrough guide book of the second game - Riven - is written like a novel.
Planescape: Torment has the Circle of Zerthimon, a history of the Gith people; reading through it and discovering what the lessons are leads to some awesome stat upgrades and spells for both the Nameless One and Dak'kon.
Baldur's Gate has around 70 different books. All are of a reasonable length alone and provide mostly non-game related information about the setting. Some are linked series, including fairly substantive histories of Shadowdale and Waterdeep.
In Final Fantasy Tactics, you can read a book full of backstory. It's pretty long for an in-game book, and even then, Ramza admits that he can't even read most of the text due to it being written in an ancient language; he's just reading a different character's notes and translations written in the margin.
Video Game/Mabinogi has literally dozens of readable books, ranging from a few pages to over 20. A handful concern game mechanics; but the majority are purely flavour text, and unnecessary to actual gameplay. Most of those are concerned with the main storyline for the game; but some are just standalone stories of adventurers, or musings by NPCs. Many are required for skill advancement, but only possession is necessary, reading them isn't.
An educational game example. The original Jump Start 1st Grade contained a modest bookshelf of in-game stories to teach young children reading. The books typically contained short stories that the game would read aloud with limited animated illustrations. Combined, there were 52 unique stories on the shelf, subjects of those stories ranging from counting, telling time, animals, caricatures of world cultures, silly poems, and entertaining short fiction, and at the end of each story the game would give a simple comprehension question at the end before proceeding to the next. Each story was an average of 3-4 pages each, the shortest stories were the Mother Goose rhymes at one page each, and the longest story was a whopping 10 in-game pages, seven at a close second. This meant the game featured a cumulative number of over 200 pages of fiction. For an educational game for first graders made in 1995, that does seem rather impressive.
- Its successor, Jumpstart 2nd Grade, only featured six stories at two pages each. The focus wasn't so much on reading the stories as filling in the blanks with parts of speech specific to the book chosen and customizing the story. This game focused slightly more on mathematics than reading, likely because the first grade game already covered that department quite well.
Golden Sun: Dark Dawn has five books, dubbed as the Sun Saga series, that retells the events of the last two Golden Sun games. You have to find said books and some of them can be Lost Forever if you go beyond one of many Points Of No Return.
Opoona has the Catalogue d'Arts, which is, essentially, a small art history textbook on the various art movements that have arisen on the planet of Landroll. You have to find the art pieces in the overworld to add them to the book, but the book gives each piece substantial backstory, and even expounds on the history of the artists who made it (such as Caval).
Dantes Inferno packed in the entirety of its source material in an autoscrolling extras menu.
Divine Divinity is chock full of those, there is at least one long series about the adventures of an ork pirate, others are about summoning demons and spells, yet others are either short stories or about the in-game world, teaching about plants, animals and monsters, or history.