The purpose of this research is to evaluate the performance of rounded and backed books against books left square backed. The variables which are introduced into the study will enable the results to provide needed information on the performance of the many different binding constructions librarians and library binders are confronted with. Rounding and backing is an optional operation when binding a book, an operation which is sometimes by-passed on smaller books. A book that is not rounded and backed is square backed. It is suspected that rounding and backing a book will indeed enhance its performance and durability, therefore guaranteeing more circulations and a longer life. The books were tested in the Dudley A. Weiss Book Testing Laboratory at Rochester Institute of Technology. The testing procedures used, the Tumble Tester and the Universal Book Tester, were designed to accelerate simulated book usage. During the destructive testing, visual observations were made at progressive time intervals to determine the effects of rounding and backing versus square backed, thus answering all the questions stated in the objectives section in Chapter 2. Upon the completion of all testing, the observations were summarized to determine what effect rounding and backing had on the performance of the books. Many very interesting observations were made. When rounding and backing a book, the ridge that is formed when bending the pages or signatures over one-another, does indeed provide added support to the joint strength and the binding. However ; to assure the best possible performance of a rounded and backed book, it is important that a uniform layer of joint adhesive is applied. A book lacking good joint adhesion will destruct much faster than a book guaranteed to have optimum joint adhesion, whether rounded and backed or square backed