The Bruce Perens' Open Source Series is a series of books edited by Bruce Perens as series editor and published by Prentice Hall PTR. Principal topics are Linux and Open Source. These books are intended for professional software developers, system and network administrators, and power users. Each book is licensed under the Open Publication License and is made available as a free download several months after publication. As of June 2007, there are 24 titles in the series.