Liber Necris
Liber Necris, or Book of the Dead (from Latin liber "book" and Greek nekros "dead"), is a source of background material describing the different kinds of Undead creatures and concepts of necromancy that appear in the Warhammer Fantasy setting. Written and compiled by "Marijan von Staufer", it was first published by The Black Library, an imprint of Games Workshop's publishing division BL Publishing, in June 2006.
Liber Necris is a fictional book written in an entirely in-setting style, purportedly by Mannfred von Carstein, one of the Vampire counts as his own encyclopaedic description of his kind.
There have been a number of books of the dead mentioned in the background material - the nine "Books of Nagash", the "Liber Mortis" of Vanhal - but none of these has ever appeared as more than passing references or small passages. Liber Necris was originally going to be written and released as Liber Mortis, from the narrative POV of Vanhal, but when AD&D released a book the previous year called "Libris Mortis" the decision was made by BL Publishing to change the name of their book to Liber Necris.
Read more about this topic: Undead (Warhammer)