Unless one manages to break into the libraries of Greyhaven, most magic tomes are found in the depths of the tombs of long-forgotten spellcasters. A tome is not simply an instruction manual on how to cast a spell. The very act of writing spells upon the page can leave some small resonance with the world’s energies, and if the reader can read and follow the instructions exactly, they can call upon that resonance to boost their own spells.
References
- Realms of Terrinoth