The collection consists of extensive writings by Klein on traditional Jewish practice and law. This includes manuscript material for his books Guide to Jewish Religious Practice (1979), The Ten Commandments in a Changing World (1963), The Anguish and the Ecstasy of a Jewish Chaplain (1974), and his translation of The Code of Maimonides (Mishneh Torah): Book 7, The Book of Agriculture (1979). Also represented are speeches, sermons, articles, and remarks from the conservative Jewish viewpoint on subjects such as medical ethics, dietary laws, adoption, and marriage and divorce. Meeting minutes, annual reports, bulletins, and sermons relating to Klein's rabbinical vocations in Springfield, Massachusetts and Buffalo, New York are also included. The papers contain photographs, wartime letters, and military records of Klein documenting his service in World War II as a director of Jewish religious affairs in Germany.