The classification system presented in this volume is based largely on Dewey's magnum opus Decimal System (1876) and Ockerbloom's excellent Free Decimal Correspondence (2010). It has been slightly updated for improved benefit to librarians. It shortens subject headings, provides a more intuitive sequence of topics, and reduces the number of classes to nine-freeing up the tenth class for any purpose of the librarian's choosing. It retains Dewey's classic preface and card catalog appendix, removes the outdated index, retains most of Ockerbloom's scope and nomenclature, and adds guidance for digital collections.