The first chapter is the most valuable. It offers broad tips for a top down debugging approach to a wireless network problem. Also, it is largely independent of specific hardware elements. You can apply the guidelines even if you have non-Cisco items in the network. Of its advice, two very good tips stand out. The first is simply to have an extensive and complete network diagram. Do this when everything is [presumably] working. Don't wait till things go wrong before amassing such a diagram.
The second tip is to imagine you are offsite and are talking on the phone to an onsite sysadmin. And no visuals on your phone. It's strictly audio. This gedanken forces you to focus on what might be the key features of the problem.
The rest of the book then delves into specific abilities of Cisco boxes. Often there might be diagnostic text output that you can get. Cisco has been careful about enabling its machines to provide copious diagnostic dumps. The mass of detail is needed because of the many possible failure symptoms. But this also means that part of the skill you should cultivate is an intuition about what to look for in a potential surfeit of a data dump.
One impression from the book is that wireless problems can be harder than those in an all-wired network. For the latter, at least in principle, you can trace the wires and test each link. But wireless transceivers can overlap in broadcast range. While evesdropping does not require physical access to your equipment by an adversary.