The Dewey Decimal Classification (DDC) is used in more than 200,000 libraries worldwide as a knowledge- and information-management system. For small school libraries and immense national collections, the enumerative structure, developed 150 years ago, is familiar yet frequently mysterious and not without controversy. In this discussion of what has become a ubiquitous tool, coauthors Kyrios (senior editor, OCLC) and Satija (emeritus, library and information science, Guru Nanak Dev Univ., India) provide a fascinating look into the history, philosophy, administration, current use, and future of the DDC, along with concise explanations of both major categories and minor subdivisions. Some of the 18 chapters that deal with the more arcane facets and number-building features of the system may be of interest only to a few; however, the way in which these details, with myriad relevant examples, are presented is engaging. While focusing primarily on the strengths of both the print and electronic DDC, the authors do not shy away from describing its weaknesses, including its systemic bias. VERDICT Both an excellent reference resource and an interesting read for Dewey experts and non-experts alike. Highly recommended for professional-development collections.