The proposed book explains the Dewey Decimal Classification (DDC) system of classification of books in libraries. Pertinent topics like Rules of Classification, Use of Standard Subdivisions, Use of Tables 2, 3, 4, and 5, and Multiple Syntheses have been taken up in the book. The text is rich with examples of classifications and notations. DDC is used by all the libraries as it has universal application. All the universities have included DDC in their syllabi for courses in Library & Information Science