Universe Compendium

A Universe Bible is something created for the writers and production team of a series or franchise. While many of these have made their way into the public arena, they are really not intended for public consumption. As a result, they often contain much which, like real bibles, is apocryphal, confusing or outright wrong.

It is therefore often necessary to distill the bible down to a terser piece, more consistent in style and more limited in scope before officially releasing it to the fans. A Universe Compendium is a book or series of books which encapsulates much of the information in the Universe Bible, reformatted for consistency, with information added or removed for various reasons: It may go into more detail than the bible in some areas, or omit information that would be considered a Spoiler.

Depending on the size of the Universe Bible, the compendium may be split into several books, each having considerably narrower scopes. They can include licensed supplements for paper-and-pencil Role Playing Games, though these just as often qualify as Universe Concordances.

Any details in a compendium which have not been established on-screen are subject to revision, and cannot be assumed to be Canon; though it's still considered bad form for fanfic writers to contradict them. Canon writers get more of a pass because they presumably had plans for the series's future long before the compendium was published, and the compendium authors or may not have consulted with them to avoid contradicting those plans.

Often, once such a book is compiled, writers will begin referring to it rather than the Universe Bible. While the Bible retains primacy, the ad hoc manner in which the Bible is maintained often makes it harder to use.

More common, and more necessary, for Speculative Fiction shows, since a show with a mundane setting just has to keep track of the protagonists and their situations.

The official counterpart of the Universe Concordance.

Examples of Universe Compendium include:

Anime and Manga

These books are almost mandatory merch in the Anime world.

Comic Books

Marvel Comics has recently started hiring especially well-known fansite creators to write their compendia on a certain series, bringing the game between a Universe Compendium and a Universe Concordance.

Film

Numerous detailed technical books have also been released concerning the Star Wars universe—from Vehicles of Star Wars to in-depth manuals on the construction and maintenance of lightsabers.

Literature

Stephen King's mythology for The Dark Tower got so out of hand that, when he sat down to finish the series, he hired someone to write him a "Concordance" summarising all the relevant information. He was so pleased with the end result that he had it published.
The Discworld Companion has been around long enough to have had two new and expanded editions.
Warriors had Secrets of the Clans, which spawned a fanmade volume chronicling the madness of the fandom, Secrets of the Fans.
The Doctor Who Spin-Off Faction Paradox has a wildy metafictional version of this sort of book, called The Book of the War.
Contacting Aliens: An Illustrated Guide to David Brin's Uplift Universe

Live Action TV

"The Blake's 7 Episode Guide", despite its name, contains a complete compendium for Blakes Seven.
Star Trek spawned a plethora of these. For each series, a "Compendium" documents the official storyline and major characters, while there are several "Technical Manuals" and other more specific guides which document the technology and standard props found in the series. One of the earliest of these was the Star Trek Medical Handbook, an official guide to medical science in the 23rd century. The all-encompassing Star Trek Chronology and Star Trek Encyclopedia contain more or less every known fact about the Trek Verse, the former organized historically; the latter, alphabetically. Of course (cynicism hat on) these were never quite up to date while the shows and movies were running: fans were obliged to pick up new editions periodically. And the partwork version (2 pounds per week for six years...) turned into an impenetrable mess of supplements, addenums, and stick-on corrections.
- There is a Federation travel guide.
Buffy the Vampire Slayer had three Watcher's Guides that are brilliant and quite comprehenisive, with annotated sections explaining the pop culture references in each episode, notable quotes, and actor interviews. Angel had something similar; this troper believes they were called "The Case Files."

Tabletop Games

GURPS, from Steve Jackson Games, has produced compendia for several literary universes. Author David Brin provided much of the information in GURPS Uplift, including data that had not yet appeared in any of his novels at the time of publication.

Video Games

The Metal Gear Solid Database
The ones for Shin Megami Tensei are particularly notable, as, in addition to the usual content, they have pages and pages of bibliography for the games. You can accuse them of being inaccurate to mythology, but you can't say it's because they Did Not Do the Research.
A lot of Square Enix games (before and after the merger) can have multiple guides for just one game. Best example would be the Final Fantasy and Kingdom Hearts series: the Ultimanias can almost have the weight of a phone book and are about the size of an average graphic novel released in the US (Japanese tankobon are smaller), filled with strategies, data on items/weapons/monsters, concept sketches of characters and locales, and interviews with key staff and/or voice members.
The number of "side material" books for the Nasuverse is staggering, containing archives of the game illustrations, concept art, interviews, and entire short stories that tremendously develop several characters (most infamously, the transition of Ordinary High School Student Tohno Shiki into a vampire assassin) which may or may not involve plotlines from possible sequels. All this, without mentioning the 'Dictionary' sections which expand the Canon into areas rarely mentioned in the original works. (Magecraft organizations, hierarchies, and systems? Alien invaders?) One particular volume, Character Material, is comprised almost entirely of completely new characters, characters only mentioned as an aside, or characters which previously were never illustrated.
Touhou has both Bohemian Archive in Japanese Red and Perfect Memento in Strict Sense in-universe documents that provide background detail to many of the characters, locations, events, and in the latter even the species of Gensoukyou.