I think the writer William Burroughs once said words to the effect that "No one controls life, but anyone with a frying pan controls death." I mention that in the context of this book because one doesn't have to be an expert in violence to hurt others, but one does need some level of expertise or training to even begin to gather the skill set to defuse a violent situation. It takes years to become a good soldier or cop, but it takes one vial of PCP to become good at violence. It's also hard to become an expert in the praxis of violence, because you can get hurt or killed (obviously) while learning. You might gain experience, but you'll also lose a leg or maybe your life. That leaves the theory of violence, then, but since the gulf between what we're taught (for combat training or martial arts) and what actually happens is so wide, how do you bridge that gap?
Rory Miller does a pretty good job of trying to teach the reader about violence, what it does to the mind, the body, and spirit. He's careful to show that even when one emerges victorious from a confrontation, there are still major consequences one must face. The book is not just philosophical, however, and it is filled with Miller's real-world experiences with the violent, the predatory, and the mentally ill. The author has experience in working security, corrections, and in studying martial arts.
That said, he doesn't try to add a veneer of Eastern Mysticism over everything he does, acting as if he's some kind of guru, which can happen a lot in these kinds of texts. Many "self-defense experts" seem lost on a Steven Segal kick, where they're as obsessed with proving their own toughness and bad-ass bona fides to the reader as they are offering helpful advice or admitting their own faults in the hope that the reader can learn from them. Rory Miller checks his ego on Page 1, and provided you're willing to meet him halfway, you'll learn something, regardless of your own level of experience with violence. Recommended.