The Krivbeknih

The  is a book added to Fallout 3 in the Point Lookout add-on.

Said to possess a dark power, it used to be in the possession of the Blackhall family but was lost long ago.

Related quest: The Dark Heart of Blackhall
Obadiah Blackhall wants you to retrieve this book from the Ritual Site in Point Lookout and return it to him, whereas Marcella wants it destroyed.

Behind the scenes
The Krivbeknih is a reference to the many esoteric and arcane tomes featured in the Cthulhu mythos, written by H.P. Lovecraft, such as the Necronomicon, Book of Eibon, Pnakotic Manuscripts, etc. These artifacts play a similiar role in the mythos, often being used by evil men for sinister purposes.

Also, the Dunwich building where you go to destroy the book is a reference to Lovecrafts short story "The Dunwich Horror", and an audio tape recovered in the building contains a reference to "Alhazred", the fictional author of "Necronomicon".