Open source software are those which permit execution, copy, read, distribution and improvement of the software without any restrictions. Library Management Software (LMS), is an enterprise resource planning system for a library, used to track items owned, orders made, bills paid, and patrons who have borrowed. Commercial library management software are very expensive. Therefore, open source library management system can be appropriate alternatives for automatic library systems. This Book discusses features of open source library management software, criteria of selection of best open source library management software, their, advantages and limitations. Open source library management software is a solution to reduce that cost. The Book describes in brief about the feature of ABCD (Automation of Libraries and Documentation Centers) of the open source library management software.