The flying books are a creation of the squid race. They developed special sets of runes to write down their psionic knowledge while encryption it at the same time. Over time they figured out how to arrange the psionic runes to create certain effects. The hovering of the flying books was the very first breakthrough in this area. In the centuries that followed, the squid race honed their skills and created a own caste of 'authors' to create weaponized books with psionic powers that emulate spells. Most of these tomes are hidden from the eyes of foreigners in their hidden enclaves. But the rather common flying books accompanied their squid masters to many of the laces they went to. The flying books are so mundane and replaceable for the squids, that they don't take great care of them and just leave them behind when they leave an area. Sometimes skillful magicians managed to re-purpose the flying books and subvert their control by binding them to their own. Though not particular more powerful then comparable bind golems the sheer rarity of flying books outside the squid community make them a prestige object for many aspiring magic users. Warnings that those books might have been just 'allowed' to be found and repossessed to allow the squids spying on others have yet to be proven and haven't stopped many from acquiring such a prestigious object. The idea that a device could constantly transmit information to its creator does nothing to diminish its popularity in comparison of the need of many to show off. That way flying books have been introduced to many places in the known world. Some failed attempts to overwrite the books initial conditioning have even lead to the creation of 'rogue' books that roam around on their own in their mindless pursuit of whatever random impulse might guide them in the moment.
Flying Books have 500 hitpoints. They cannot be paralysed. Moreover, they are strong against death, earth, energy, fire, holy, ice and physical damage. These creatures can neither be summoned nor convinced. In addition, they are able to sense invisible creatures.
Flying Books yield 200 experience points. They carry nothing with them.