VoIP is a technology that has been touted as the "Next Big Thing" for at least 10 years now. All but a few slow cases in the marketing department have now realised that it is a technology with a slow and gradual take-up and is never going to be a gold-rush. There are three main areas where VoIP has made some in-roads: Technology savvy computer users taking advantage of cheap or even free long distance calls over the Internet, companies replacing aging voice or data infrastructure using the upgrade as an excuse to converge their communication and data networks, and large telecom companies replacing their core networks. Add to this the companies developing and manufacturing VoIP equipment and we have four diverse domains with very different requirements, constraints, budgets, and understanding.
From this fragmented VoIP world I have failed to identify the target audience for this book. The large telecom companies and equipment manufacturers are too close to the bleeding edge to benefit from printed source material that is at best several years out of date due to the long lead times in book publishing.
Most of the book's hands-on technical content concerns the Linux-based Asterisk PBX (Private Branch Exchange) application and covers installation, configuring and programming. The interface equipment required is only available through specialist suppliers and the small market makes it relatively expensive, limiting its appeal to a few hard-core Linux fans. The technical detail is too low level for most commercial organisations and the sections aimed at this audience, such as RoI estimates, are too few and far between to be worth buying the book for.
The author does provide a good grounding in VoIP concepts, and even has several chapters that are good tutorial material. Unfortunately this is interspersed with the Linux-Asterisk specific detail so that using the book as an introduction to VoIP is difficult. The material is also very US-centric limiting its usefulness to those not working in areas of the world using ANSI telecoms standards, this despite the author claiming otherwise in the introduction.
Overall this book tries to do too many things on too many levels and fails to achieve any of them. The author is obviously very knowledgeable on the subject and the content matter of the book is good. It is just that that it does not all belong together in the same tome. The Linux-Asterisk part needs its own dedicated book, as I believe it has. The tutorial on VoIP needs to consider a non-US audience, and to drop the advocacy, resulting in a much slimmer volume. Finally, there is a need, only just touched on here, for a good guide for the SME thinking of moving to a VoIP and covering the solutions available off-the-shelf and not DIY.