This is not the best book on the subject I have -- it has an exclusively U.S. coverage and gives the impression that the author thinks that telecoms is the same the world over. An example is the very first definition in the book: it is for "0", which it defines as "The 'in fact' standard number to dial for reaching a local phone company operator or answering service." Some of the definitions are not quite right (e.g. that for a Terminal Adapter), some are not clearly written, and some are missing (e.g. "firewall" is absent, although "relational database" is present).
The pictures are helpful, but are sometimes fuzzy, and overall it seems in need of a good edit. I guess it's grown over its three editions, and has now become rather unfocused.
The CD is just an Acrobat version of the book. It's not "fully searchable" as claimed.
I much prefer -- and will use much more -- the excellent "Computer Dictionary -- Data Communications, PC Hardware and Internet Terminology" from Mitchell Shnier (Pub. Que).