I really wanted to like this book.
The first few chapters give a quick summary of networking and TCP/IP basics. It's a subject which is difficult to cover so quickly. I'm not sure Sanders does it justice, to be honest--if you aren't already familiar with the concepts, I don't think this would be an adequate introduction.
The next few chapters discuss the mechanics of using the Wireshark program itself. I appreciate this section, as it taught me a few simple but very useful features of Wireshark that I had overlooked.
The bulk of the book presents a few packet capture use cases, and guides you through the analysis. You can download the .pcap files and follow along, and I encourage you to do that. Some of the examples can be puzzled out from the packet captures alone, and these are pretty fun. Unfortunately, a lot of the examples are only given a superficial treatment. I already knew that bittorrent traffic can consume a lot of bandwidth and will go all over the place, and the idea to look for the word bittorrent in the traffic itself is not all that insightful.
But the real letdown is the errors: the first printing has a ton of them. Things like the wrong diagram, or a packet trace that has obviously incorrect MAC addresses. On Amazon, the author says that many of these errors were corrected in later printings, but that doesn't help me. As of today, a year after he made that comment, there's still no errata for the first edition on the No Starch Press website.