Open Letters Monthly has an article called In Defense of the Memory Theater, by Nathan Schneider in which he argues that books on shelves perform the function of reflecting memories back at us. They are a constant reminder of the various events, stages, and emotional states of our lives. We look at our shelves and can instantly catapult ourselves back in time to events surrounding our reading of various volumes.
Schneider mentions a 16th-century memory theater that used images and symbols of the cosmos to inspire observers and enhance their intellectual powers. Books, for Schneider, do something similar when they are visible on our shelves. I agree up to a point. I am often taken back in time by my own books upon their shelves. But so am I transported by nearly every object in my home. Objects all have this power. Books are not exceptional in this regard.