This book covers networking "soup to nuts" -- you'll learn not only about networking concepts and devices and protocols, but also how the hardware and software are designed to do it all efficiently. It was, for me, a bit mind-opening. They cover the architecture of switches, network interfaces, etc., protocols for packet classification, link scheduling, etc. -- at every level of a network they explain the issues and move you from a naive implementation toward how things are really done. They even cover chip design and specialized operating systems for routers.
There are a few things you should know. First, the book makes no attempt to be chatty or friendly -- it is a densely packed, no-nonsense treatment of a lot of material in just 300 pages. It is a bit dry, but well written. Also, if you actually need to implement something -- e.g a router or a protocol handler -- you will need more than this book. Think of this book as going deeply into the *concepts* for a broad range of networking topics, but not so deep into the implementation that you could actually create what they are talking about.
One thing I really like about this book is its very generous use of diagrams. If you are a visual learner, you will like this book. There is still some room for improvement, e.g. in some cases the diagrams depend too much on information buried in paragraphs above. For example, in a diagram explaining the use of hierarchical trees for packet classification, the diagram should really state that we are trying to match 1010/0111; because it doesn't, I was confused about what the diagram was depicting until I found where they established the context for the diagram on the previous page. But despite minor issues with assuming too much context, the diagrams are well thought out and add greatly to the presentation.
It's an excellent book, and I learned a lot from it.