Oxford doesn't publish books for "dummies" -- they publish "very short introductions". And this one isn't for dummies. It's an informed overview of the elements of understanding risks and making decisions with respect to them.
For most of us, risk is something we address in an informal, rule-of-thumb manner. I think this goes for everything from the risks we run in leaving our homes every day (or even staying in them), to how we invest our 401ks, to our willingness or unwillingness to participate in dangerous sports like rock-climbing or ocean swimming, and even to business risks arising in our professional lives. We trust in our own decision-making, often with little information to go on.
We certainly pay a price. For example, if we rely on the flow of information we simply happen to receive, we over-estimate our vulnerability to violent crime, natural disasters, traffic accidents, and the like. Our information flow isn't designed as an unbiased source for risk assessment.
The authors have made careers of understanding risk. The most interesting point they make, I think, is that "societies reveal themselves by how they handle dangers." How we measure risks, including what it is that we consider risks to be risks to reveal, in action, what we value, what really matters to us. Is it life, simply put? Is it a life of a particular kind? Is it long life? Is it healthy life?
"Very short introductions" are not for professionals -- they are for the majority of us who can benefit from an explicit, reflective framework for something we don't really have an informed way of thinking about. Maybe the most valuable thing we can learn is that there are, in fact, informed ways to think about and make decisions with respect to the risks that are ubiquitous in everyday life.