Twenty descriptive case studies of computer applications in a variety of libraries are presented in this book. Computerized circulation, serial and acquisition systems in public, high school, college, university and business libraries are included. Each of the studies discusses: 1) the environment in which the system operates, 2) the objectives of the library and the system, 3) the computer equipment and programing used, 4) what the system does and how it operates, 5) the costs involved, 6) aspects that should be considered by librarians who are wondering whether a computer system would meet their specific requirements. A final section summarizes the salient features of each type of system and comments upon them. Some major practical reasons are given for automating library functions: to do something less expensively, faster or more accurately, to do something that can no longer be done effectively manually, or to do something that cannot be done manually at all. (JG)