Amazon.com just posted my four star review of Voice over IP Security by Patrick Park. From the review:
The reviews of Voice over IP Security are fairly consistent at 4 stars, and I agree with that consensus. I've read a few books on this topic, and early titles were fairly awful. My favorite remains Hacking Exposed: VoIP, but a comparison with Voice over IP Security shows different audiences for the two books. The HE book is better suited for those assessing VoIP systems, while this book is better for engineers and those implementing VoIP systems.