Watching Asterisk move from being a personal coding project to a community of tens of thousands of programmers and millions of users has been quite the ride so far! Asterisk is only now hitting its prime, and there are so many more things that creative people are going to do with the code. The growth of the project over the years has stunned and pleased me, and it's amazing that well-written and comprehensive books like this now exist to help more advanced users navigate the waters of larger and more complex Asterisk installations. Asterisk installations are now huge, both in numbers of locations and the unimaginably large size of many of those locations—thousands or tens of thousands of users! Asterisk implementations are rarely limited by the capability of the software but more often by not knowing how to utilize it. Books like this play an important role in getting the experience of those who have already done in the hands of those who want to do.
Hopefully the knowledge here allows you to continue your adventure with Asterisk, moving from the basics of PBX construction to having the ability to quickly implement advanced call logic processes and work with the more exotic telephony and VoIP interfaces. The motto of "There's more than one way to do it!" is almost always true with Asterisk—this book seems to contain an excellent cross-section of at least one of those ways to do "it" (whatever "it" happens to be for your application) and you'll quickly think of many other ways once you've mastered the methods shown.
The authors here have really shown some excellent detailed explanations of how to use Asterisk, and I hope this provides the incentive for you, the reader, to experiment in more wide-ranging ways with Asterisk once you've understood the basics. Most of the Asterisk community has learned with hands-on experimentation, and it's great to see more encouragement of this type of learning as is contained in these pages. Kudos to the authors, especially David Duffett, who has been involved with Asterisk for so long and has taught so many people their first dialplan routines (and hopefully has left them uninjured from his famous habit of throwing candy at people who give correct answers in class or in his talks).
Soon you'll be doing least-cost-routing, integrating your instant messenger system with your mobile phone calls, controlling robots with voice commands via your phone, or dreaming up a new company based on some voice-based service that nobody has tapped into yet. And the best thing about Asterisk is that it remains open source—if you come up with a feature or enhancement that you think must be in Asterisk, then the good news is that it can be! Become a member of the Asterisk community, and your contributed code could be included. We all anxiously await your book, your product, or just your involvement with the Asterisk community.