Spent this evening reshelving books (picture in the link below) when this question occurred to me. "Most value" does not necessarily mean what would fetch the most money if sold, but rather something that is a joy to you for having owned. It could be a first edition of a favorite writer, an autographed copy of a volume by an author you enjoy, a treasured heirloom from previous generations. Or it could be a whole bunch of books, like the ones in the picture in the link below.
Just curious. Oh, and if you have photos and can link them here, I'm sure that would be cool to most who read it
Je suis méchant.