The protagonist Colin accidentally became the new administrator of the "Tower of Illusion" and was trapped inside.
Learn to use library rules to protect yourself, and borrow forbidden knowledge to a limited extent (only copy the parts you can understand/bear).
Drive demon lords crazy with "little bits" of Abyssal knowledge; drive cultists away with "fragments" of ancient god rituals; create gadgets with "principles" of lost technology. The outside world regards it as a mysterious and taboo existence.
Deal with thieves trying to break in, knowledge tokens running out of control. Discover the secrets of the library itself and the fate of its past administrators. The cool thing is to have the power of "nuclear button" deterrence and knowledge
