The opening question is indicative of the type of topics discussed. The answer, it turns out is that whether you start with Cardio or Weights depends heavily on what you want to achieve: your body can either improve the circulatory system or strength, but not both, so which one you start an exercise session with determines whether or not you build strength or aerobic fitness. This is a counter-intuitive result, and therefore worthy of attention.
Running is given extra attention, as is weight lifting. You'll get interesting answers as to whether you're lifting heavy enough weights, or whether your cardio workouts are intense enough. What's good about the book is when it steers into areas that I always wanted to know but never bothered to find good answers to because Google searches would only turn up advocate's results. For instance, I've long suspected that Yoga doesn't actually do anything good for your body compared to actually doing cardio or weight lifting, and this book confirms that with references to literature.
Where the book covers topics I had previously read about elsewhere, it doesn't contradict well known existing literature. For instance, it points out that your spouse is the biggest influence on your exercise habits. It also shows that if you want to stay young, "vigorous aerobic exercise makes your DNA look several decades younger than it is. And that's bad news for the sedentary groups." In recent years, it's been fashionable to dismiss exercise as useless for losing weight, but the reality has been that exercise is important for reasons more than losing weight:
Only the diet-plus-exercise group had significant improvements in insulin sensitivity, LDL chloresterol, and distolic blood pressure---crucial risk factors for heart disease and diabetes, but changes you can't measure by looking in the mirror or stepping on a scale... (Pg. 157)In addition, the author takes on the typical prescriptions for exercise as being too little to even maintain your weight and not gain weight: "Managed to avoid significant weight gain throughout the study, and these women averaged a full hour of moderate exercise every day. Anything less was unusuccessful. That's a lot of execise---unless you compare it to the daily lives of our ancestors who didn't spend most of the day sitting at desks or in cars." (Pg. 160)
Overall, this is a good book, and given how short and easy to read it was, well worth your time. Recommended.