Unless you are specifically referring to this book and then literally using it in the field of organizing group improv games either to reinforce team building or to organize a set list for an improv show, this book is not really worth getting into it. In other words, reading it for the sake of reading it is pretty useless.
Not to blow myself up too much, but I have a more vested interest in group improv than the average person. I've been doing improv off and on for the past ten years, and recently passed the core curriculum at Upright Citizens Brigade - LA. But despite this core background in improv, even I found the page to page reading experience boring and a little alienating.
The bulk of the book is a list of improv games, including diagram-like descriptions of where the actors go and what they do. It's written very coldly, and the process is repetitive as it just leads in the same thing over and over again.
I'll admit that I'm probably being unfair, as it is described as a "manual" in the subtitle, so expecting a great reading experience is maybe not the point. But the little bits of quality writing in there, as small and disappointingly lacking as they may be, lead to expecting more than just a blueprint in a book.
The highlight of the book is Charna Halpern's explanation of tag out games. She's unfairly listed as an "additional material author" here for basically a few reprinted paragraphs that I believe I read in her far superior book "Art By Committee" which was much more philosophical in nature than this book. But her little bit here is still better prose than Gwinn's manual writing, and worth looking at.
And I can't really say I dislike Peter Gwinn's brief paragraphs, largely in truncated introduction and conclusion phases, about the importance of both improv teams and more general/corporate teams in the qualities that the games are supposed to help with, things like bonding, focus, awareness, energy, etc.
Talking about these qualities and why they're important to a team is hard to ignore, and it makes you feel like Gwinn understands the basics of human interaction and cooperation. It's good enough to raise this rating from a 1 star to a 2 star, but it's also pretty generic in its way, and like I said, its few and far between with these robotic descriptions of improv games.
For some people, reading this book is the best way to see improv games tick. But I would definitely recommend the much superior Charna Halpern "actually written by her" books "Truth In Comedy" and "Art By Committee" for a more involved reading and improv philosophy experience.