The manual does a nice job of describing what the various settings are and how to change them. But, it would be four times as long if it went into detail on the why, where, or when. Yes, beach mode is supposed to be for beaches, etc.... Park 2 is good for finding fine jewelry in dense shallow trash, etc...
In other words, people are interested in how-to books like this because they're looking for recommended settings and techniques for very specific conditions.