Panoramisk / The VoIP druid 

For those of you not yet really familiar with Asterisk or like me who wants to have the appropriate book to refer each time it is necessary, the second edition of “The Future of Telephony” is now available. If you could only buy one book on the Asterisk topic, this one is probably the best choice, a must read prior any installation or IP telephony project.
For more information, the O’Reilly site is the good place to go next.