A bookcase, or bookshelf, is a piece of furniture with horizontal shelves, often in a cabinet, used to store books or other printed materials. Bookcases are used in private homes, public and university libraries, offices and bookstores. Bookcases range from small, low models the height of a table to high models reaching up to ceiling height. Shelves may be fixed or adjustable to different positions in the case. In rooms entirely devoted to the storage of books, such as libraries, they may be permanently fixed to the walls and/or floor.

Around the time the codex emerged in the first century AD, open shelves which now housed two clashing forms, the long cylindrical scroll and the flat rectangular codex began to be considered hideous. Texts were sent into hiding, stored in armoires and trunks, which were convenient for transporting books, but not for accessing them. For the next fourteen hundred or so years, books, as Henry Petroski, a professor of civic engineering and history at Duke, writes in The Book on the Bookshelf, were shelved every which way but straight up, spine out. Engravings of private studies show books piled horizontally, standing on the edge opposite their spine (their fore edge), as well as turned fore edge out.