The Book

The Book is a supernatural book desired by different parties of ability users. It is said that anything written in the book becomes reality. Its whereabouts are unknown, however many say it is sealed.

Appearance
The Book's true appearance and whereabouts are unknown. However, it is said that its pages are all blank.

History
Very little is known of the Book. It's rumoured that it was part of an unknown ability user's power.

Summary
The Book has yet to be seen. Fitzgerald mentions it to Atsushi Nakajima, whom he claims is the 'guidepost' to the book itself, as it is located in Yokohama. Fitzgerald intends to use the Book's power to revive his deceased daughter, in hopes of improving Zelda's mental state and restore his family.

Fyodor desires the Book as well. He intends to use it to eliminate ability users as a whole, however why he wants to do so is unknown.

Decay of Angels succeeded in stealing a page from the Book from Chief Taneda. With it, they wrote a scenario to frame the Armed Detective Agency for a large hostage-murder situation, resulting in Nikolai Gogol's apparent death and the ADA as scapegoats for the attack. This is the first time the Book's power is confirmed true.

Abilities
The Book is full of blank pages, all able to alter reality even if torn out of the Book itself. However, it has some restrictions, likely implemented by its former user: According to the BEAST universe, the Book acts as a "melting point" or "centre" of multiple universes. That said, when one writes the events of a different universe into it, then that reality will replace the root universe's respective events. Altered memories may be a result of the root universe's residents being affected by the memories of a different universe, hence the universes meld to a point.
 * Only a few sentences can be written on each page.
 * As a story, the Book's contents must follow rules of karma.  This means that extreme statements, such as "All of humanity will be destroyed", cannot be brought to reality.

This brings light to the Book's limitations. Presumably, if an event has not happened in any of the other universes, it is not possible to bring into the root universe.

The Book's effect on BEAST's Osamu Dazai is minimised. Thanks to No Longer Human, Dazai is largely affected by the memories of himself in different universes, giving him an overwhelming amount of knowledge on the variants of different events.

Although the main events are referred to as the "root universe", this does not make it the "original universe", as the book allows all universes to coexist and separate. "Root universe" is used in order to avoid confusion.