The Crookstaff family library - it's almost a cliche. Of course a family of wizards would have a library. A beautiful, sun drenched library with skylights in every room. Tragically, the library is entirely empty, and has been for generations.
Then there were the wizards who forgot to "return" books to the library altogether. And students sneaking into the library at night to steal books Gradually, each wizard opted to remove books from the commons and to create their own personal library. Finally, the whole thing was privatized.
Then the library was sealed. It is said that when the stars are right you can still see the ghosts of long-passed scholars looking for the missing books.
So today, the Crookstaff clan house has many different libraries - each off limits to all but one wizard and their apprentice.