You were raised alongside an impressive library that contained a wealth of different books and you spent a lot of time in that library, as though it were your best friend. You still have that library today and spend a lot of time going through it. (Variations of this can be a specific individual's library)
Know facts associated with the type of library your family(or somebody else) would have had.
Have access to research materials of the needed types.
Distract you when you should be focusing on other things. (Wow, it's a first edition. I've read it in my families library but ours was only a second edition.)
Have you act according to your 'book knowledge' rather how things really are. ("But I read it in this book that female vampires are not as dangerous!")