I found this book very helpful in understanding what is increasingly an ubiquitous but invisible part of the infrastructure that make up the world that we live in. Being in product development, I needed a book to help make sense of all the different means for networking. This book presents that information in a very intuitive way, and helps the reader understand future advances in networking. This is written at a level for the technical staff who may need to understand this topic enough at a functional level but not at the administrative/operational level.
The section on secure communication was what I needed at the time I purchased the book, but the book's organization, level of detail and readability will definitely make this a popular reference book.