Apache™ Subversion® (SVN) provides free documentation. We recommend the extensive documentation in the SVN book "red bean". In addition, there are also books available in book stores about this subject. However, you should pay attention that books correspond to the current SVN version.
For more information, see:
Version control with Subversion: http://svnbook.red-bean.com/en/1.8/
Server-relevant chapters:
Official FAQ: http://subversion.apache.org/faq.html
(recommended as a supplement)