The Revelations of Glaaki
From Tatters of the King
The 'Revelations' was a thick hand-written book compiled over many decades by members of the Goatswood cult. It was the book that taught Hillary Quarrie the worship of Shub-Niggurath and was also studied by Malcolm Quarrie.
Atkinson was one of the recent contributors to its contents.
The wisdom, and horrors, contained within this tome were apparently lost when Hillary burned the book to prevent it from falling back into Atkinson's hands.