The Book of Spells
The Book of Spells is a book owned by Cybele in Mario and the Incredible Rescue. Prior to the events of the story, it is stolen by Bowser to conjure ghosts for his army.
As Mario and Luigi head to confront Bowser, who has already used the book to summon ghosts and kidnap Princess Peach, they become sidetracked and find Cybele in her cottage. In exchange for a coin Luigi had recently collected in the Kero Sewers, she informs them of her book being stolen and used for Bowser's scheme. The ghosts can be defeated only by collecting six mushrooms throughout the Mushroom Kingdom, marking the start of this adventure.
Though it may be assumed Cybele had her book returned to her in the aftermath, the novel actually ends with Mario receiving the book upon defeating Bowser and rescuing Peach, with Cybele seen smiling as he places it into the pouch.