Both this and its predecessor, "What Cops Know," are excellent collections of first-hand experiences of Chicago police. They're rather dated by now, having been published in the '80s and '90s, but I suspect the basic emotions and descriptions are not that different today. They certainly will not make you want to run out and be a police officer, but they do present a candid view of the job that makes you appreciate the people who are willing to do it, and respect the professionalism of those who do it well.
The whole book is basically snippets of conversation Fletcher had with different officers. You get to hear cops being frank and candid. This book predates the era of ubiquitous video cameras and even body-worn cameras, so many of the dynamics have changed. Still this is a useful and informative book. Check out the two companion books, also from this same author.
The first book, What Cops Know, still fascinates me. However, this book is really quite dated, in that technology has moved on significantly since the 80's, and most of their 'worst fears' have been far surpassed. Yay us? :-(