In this engaging book, two top particle physicists explore the discovery of the famous equation E = mc2 by Albert Einstein, and its meaning in modern theoretical (and experimental) physics. Specifically, they address its role in defining mass as a form of energy, and how it is rooted in the search for unchanging values in the unified spacetime inherent in the theory of relativity.
The book tackles some weighty issues, which certainly isn't unusual for a theoretical physics book, but one of the key features of this book is that the authors never lose sight of how important it is to confirm theory with experiment. Nor do they forget that the average reader doesn't care about esoteric concepts - they want to know why the theories are important in their lives. The physicists certainly address this concept.
If there was a flaw in this book, it's that it was written for too broad an audience. There is some mathematics (which will deter the mathematically challenged), but in deference to the mathematically challenged the discussion is very basic (which will deter the mathematically unchallenged). The authors are clearly aware of this, and even apologize in the text to both of these groups. This comes up at other times - the sometimes-folksy (British folksy, that is, like Monty Python explaining particle physics over tea) prose can cause the reader who wants a clear explanation to get frustrated.
In other words, this book is best suited for the artful reader, who likes beautiful language more than mathematics, but is willing to tolerate some equations and be unintimidated by them. But for such a reader, who has likely not explored the core principles of physics in great detail, there is a whole new universe that can be opened up in the prose of Cox & Forshaw ... and it's a beautiful universe about which, as they say, we should all care.