The Black Book of Silly Magic is an occult collection of ancient chronicles, treatises, and instructions on occult rituals and spells of Silly Magic. Although we do not know the scholar that wrote this book, it is thought to contain treatises of various forms of silly magic from Edward, instructions on setting up occult rituals and how to perform different spells by the Wizard Of Spells, and chronicles from multiple sources such as Pobis, The Eeper, The Mimir, Plimpus, and Kiw. It was used to understand what happened before the creation of Silly Planet, and why we know so much about Bingus' Betrayal.
History[]
In the first timeline, Wizard of Spells kept the book within Ristle Cave, the same cave that The Beast was released from during the fight between Billy and Bentley. Later on, Glinkert stole the document and travelled back in time to show it to his younger self.
In the canon timeline, the book handed to Glinkert by Future Glinkert was used to start a cult called the Cult of The Black Book of Silly Magic. The first members were Bat Cat, Slorphus, Demonic little Grey Cat, Wizard of Spells, Grinwatcher, and Pobis. After the Grinwatcher took over the cult and turned it into a terrorist organization called the Cult of The Grinwatcher, and later during its combination with B.A.D, the book soon came between the hands of different members.
First, it came into the hands of Glinkert. From Glinkert's common fights with Future Kitty, Future Kitty eventually was able to replicate the manuscript multiple times, creating secret copies of the book, which he would give to other kitties in The GOODings such that the timeline can stay good.
Then, by some weird operation, it fell into the hands of Pobis. The Grinwatcher saw his opportunity and stole the book. The Grinwatcher gave it to his right hand man. The SBI came to know about it and ambushed Right Hand Smiles. The book stayed in their catalogs for quite some time, until Glinkert took the book and travelled back in time to give it back to his past self to keep the timeline continuum.
There is a confidential document below from the SBI detailing other things in relation to this. Proceed with caution.

On the 13th of December, 2023 Pobis was interrogated. Through the interrogation it was found where the book was. Pobis told them that after the Grinwatcher stole it he had given it to his right hand man, Right Hand Smiles. 2 weeks later on the 5th of January, 2024, Right Hand Smiles was ambushed by personnel and the book was confiscated. The book was thoroughly researched and the way to summon many dangerous entities was found. The book was a gold mine of research. The book has been cataloged into the main library and is kept in a locked safe.