Are you thinking about building an Asterisk PBX?

"If you are thinking about building an Asterisk PBX, but don’t know where to start, then Building Telephony Systems with Asterisk is a great book to start with. Don’t be surprised by its small size, this really is a great guide to getting started with your first Asterisk PBX system.

http://www.packtpub.com/asterisk/book