I wanted a quick reference guide that was complete enough to actually program routers and switches ... not theory. 90% of the time I have a question, I can get it answered from this book in less than a minute. So, five stars from me.
No guide will be perfect for everyone. This is not a textbook and not for learning. Great lightweight reference and for review of a topic. Good style and clean layout, but not exciting. The Index in the back of the book WORKS.