The back of a book is an important part of the book, as it contains information that can help readers find what they are looking for. The back of a book includes an INDEX, which is an alphabetical list of topics and page numbers; a SPINE, which is the vertical edge of the book that holds the pages together; and a dorse, which is the blank side of the paper used to print the book. All of these components are essential for helping readers navigate the book and find the information they need.