For a pocket reference, this is a good book. It covers all the relevant subjects, explains the issues concisely, and provides ample pictures to illustrate points.
However, there are several pictures that are wrong -- they show the wrong device for the explanation.
Secondly, a "pocket" reference simply can't contain all that much information.
Nevertheless, given the fact that this is a pocket reference, it is valueable in providing concise and relevant information, and it covers a wide range of topics that are important.