I enjoy having bookcases even if I only occasionally pull out my favorite books.  My own bookcases are home to photo albums, memorabilia, a microscope, and even a few books.  We have bookcases all over our 1790/1870 home.  Some of our bookcases will only hold narrow paperbacks and others are deep enough for our biggest volumes.  In my mind, there are few rooms that do not benefit from a great bookcase.