Plasmanomicon

Jenny's human date giving her a copy of the book.

The Plasmanomicon was a book of eldritch lore, written by “a mad Arab, or something”.

Only three copies of it existed in its universe, where a young man sold his soul to a Hellhound in exchange for one of the copies, which he intended to gift to Jenny Everywhere as a Valentine's Day present. (COMIC: My Bloody Valentine)

Reading an incantation in Sanskrit aloud from the book later led Jenny's shifting to misfire, landing her and David in the realm of the god Shiva, who confiscated the book and sent the two on a mission on his behalf. When they returned, Shiva gave the book back to them, stating that he was unsure of its worth as a magical tome but had found it “most entertaining” as a work of fiction. (COMIC: Soulless Mate)