Spurious Book appears during the first Full Moon Operation, blocking the party's progress towards the front of the train and Arcana Priestess. It will later appear in the upper half of the first section of Arqa Block in Tartarus as a normal enemy.
Spurious Book also makes an appearance in the first half of Malebolge in the Abyss of Time, with altered capabilities.
Persona 4
Spurious Book appears in the 3rd and 4th Chapter of the Void Quest in the Midnight Channel. Upon being defeated, they may drop the Paleograph material. Selling 10 Paleographs at Daidara will unlock the Healthy Recipe accessory in the shop's inventory, which helps prevent Exhaustion.
In Golden, it appears on Chapters 2 to 4. It may also drop Olive Stone for trade at Shiroku Pub.