Content Warning: This section of the guide includes discussion of emotional and physical abuse.

The first three pages of the book are excerpts from the journal of Stanford Pines, the author of the three journals in the Gravity Falls universe. Stanford was influenced, controlled, and tortured by Bill Cipher, the protagonist of this book and the antagonist of Gravity Falls, for decades. He writes that he worries Bill is not actually dead after his defeat and petrification at the end of his temporary apocalypse, Weirdmageddon. Stanford and his twin brother Stanley have tested Bill’s statue and thrown away any remnants of Bill’s existence, but Stanford is still afraid his memories of Bill could return after being erased by the Memory Gun, bringing Bill with them.

While packing for a family trip, Stanford finds a black book with a triangle; despite believing it is a prank, he throws the book away, shoots the trash, and throws the trash in a ravine. Despite his efforts, the book continues to return to him unscathed, forcing him to acknowledge that it is the Book of Bill. The book is magical and created from “brain matter,” and it allows Bill to communicate with others after his death on the changing, manipulative pages.