Often souvenir books are considered ephemera: Most libraries do not purchase them. Sometimes, however, they take the form of a book of articles by notable authors; these are treated as essay collections by libraries and by RILM. For example, the souvenir book published by New York’s Metropolitan Opera for their 1988 production of Wagner’s Der Ring des Nibelungen includes contributions by the musicologists Carolyn Abbate and Barry Millington and the poet and literary critic Richard Howard.
