The Return of the Sorcerer ties into the book of magic appearing in stories by which horror writer?
The Return of the Sorcerer: "The Return of the Sorcerer" is a horror short story by Clark Ashton Smith, first published in "Strange Tales of Mystery and Terror" in September 1931. The Return of the Sorcerer:  The story ties into H. P. Lovecraft's Cthulhu Mythos due to its references to Lovecraft's invented book of occult lore the "Necronomicon". Necronomicon: The Necronomicon is a fictional grimoire (textbook of magic) appearing in the stories by horror writer H. P. Lovecraft and his followers.
H. P. Lovecraft