Don't expect the book to tell you what a gesture means in every part of the world or to show you every gesture used in some part of the world. The book of course doesn't do such a hard task, though it tries: it explains you the gestures that are generalized (or most common) in a country. However, be always aware that there are exceptions and gestures you should know and are not included in the book.
Below are some questions you'll answer reading the book. In some cases the book gives you also the explanation about the gesture (what it comes from).
Where should you avoid the "OK sign"? Where should a man enter before a woman? Why Latin people get closer to you when talking? How should you bow in Japan?