A lot of backgrounds of contemporary or generally modern settings can be make-or-break with some of the smaller details, the way crowds and passerby are posed and move, etc.

A lot of that stuff also isn't super exciting to draw because you don't want to detract from the focal point of the art or the central character, but when it's not done well or just generally left out, it's noticeable! Some of the foremost manga and comic artists make subtle but great use of these techniques and I think this is a very useful book. A few step-by-steps are weaker here or there, but for the most part it's very strong and easy to follow.