Books can be useful and they can be valuable, and wizards and mages in particular can have valuable books related to magic on their shelves. Not every such book in a wizard's possession will be of truly outstanding value, though; the majority will be lesser books of lesser value, and this supplement has 100 books on subjects of interest to such types to flesh out their bookshelves. Whether or not any book contains information that is useful or valuable is up to the GameMaster. In a fantasy setting, even a book of lesser importance on the subject of magic will still have value, with a suggested price of 2d6 gp per book. They do not have to be books either, as these could also be found as scrolls, or perhaps clay or stone tablets. In both cases the value would be reduced and in the latter case the tablets would be much harder to transport, and much heavier.
- from the publisher's blurb