A public bookcase (also known as a free library or street library or sidewalk library) is a cabinet which may be freely and anonymously used for the exchange and storage of books without the administrative rigor associated with formal libraries. When in public places these cabinets are of a robust and weatherproof design which are available at all times. However, cabinets installed in public or commercial buildings may be simple, unmodified book-shelves and may only be available during certain periods.
If a public bookcase is centrally and accessibly located and is stocked with sufficient material, public bookcases are quickly and widely appreciated. Vandalism has occurred in some places and, in successful cases, is countered by “bookcase sponsors” or “godfathers” who devote their time and attention to care of the collection.
The acceptance, motivation and user-profile of public bookshelves was examined in 2008 by a study at the University of Bonn.
 It was found that the system had developed as a notable alternative to conventional bookstores. One cannot equate public bookcases with classic peer-to-peer exchange, but they certainly represent the voluntary transfer of goods. Surveyed users also indicated that they believed that regular use of public bookcases could function as an example for similar schemes for other desirable goods. This acceptance has led to a rapid dissemination of public bookshelves throughout Germany. It has been found that durable construction and storm-resistance promote sustained use.
In North America, public bookcases have been criticized for being mostly placed redundantly in neighborhoods of wealthier well-educated people, where there are already high-quality traditional public libraries nearby.