This book is great for those people who are just beginning their workout journey. I have known about HIIT workouts for years, and I have consistently been surprised by their results. I am not "ripped," nor do I have a six-pack, but I do notice results every time that I train in intervals.

The only criticism that I have of this book is the science that pertains to psychological attitudes towards HIIT workouts. The author cites a study by one of his own grad students, which is, to say the least, the easy way out. The fact is, HIIT workouts are hard, and are (in my opinion) not sustainable over the course of an entire lifetime. I would like to see more studies about long-term attitudes towards HIIT workouts in order to corroborate the findings of the studies that the author lists. In my personal experience, I only have used them in order to lose weight initially, and also to break fitness plateaus.

That being said, this book is a good primer for those who want to know how to structure interval workouts, and the author gives several examples of what the workouts look like. Would recommend to anyone who is feeling lost in the fitness world and wants to try something that may be new to them.