A bookcase is a piece of furniture with shelves that you keep books on. a piece of furniture with shelves to hold books. Piece of furniture fitted with shelves, formerly often enclosed by doors. In early times the ambry, or wall cupboard, was used to hold books. Bookcases were included in the medieval fittings of college libraries in Britain. The earliest dated domestic examples were made of oak in 1666 for the diarist Samuel Pepys