The Library didn't only contain magical books, the ones which are chained to their shelves and are very dangerous. It also contained perfectly ordinary books, printed on commonplace paper in mundane ink. It would be a mistake to think that they weren't also dangerous, just because reading them didn't make fireworks go off in the sky. Reading them sometimes did the more dangeous trick of making fireworks go off in the privacy of the reader's brain.
Terry PratchettHe said it was better to belong where you don't belong than not to belong where you used to belong, remembering when you used to belong there.
Terry Pratchett