One of the most important scientific stories of 2008 has been the calculation of the heavy particle masses (“hadrons”) using some of the most elaborate computational methods yet. This has been yet another vindication of Quantum Chromodynamics (QCD), a strange theory that governs the interactions of particles that make up atomic nuclei. This theory is a cousin of electromagnetism, and like the theory of electromagnetism it is deceptively easy to formulate (at least with the aid of some higher mathematics), but the real-world predictions have been devilishly hard to extract. One of the earliest people to show that QCD does in fact correspond to physical reality was Frank Wilczek, who remarkably did this important work while still in his early twenties. Since then he has gone onto an illustrious career in theoretical Physics that culminated in his winning a Noble Prize for his work. To people in the Physics community he has been known for many years for his lucid expository articles, and we are all fortunate that he has written a book about some of the topics that he is the foremost authority on. The basic premise of this book, as suggested by the title itself, is that most of the stuff that we are surrounded with is in fact trapped energy. Wilckek turns the famous Einstein’s equation E =m c^2 around, and in the form m = E/c^2 shows the rationale for why we can have mass as a form of energy. His writing is clear and accessible, and the book is not burdened with the technical details. Even so, many places could potentially be obscure to people who are not familiar with the basic ideas of modern Physics. Overall, however, this is one enjoyable and interesting book and a worthwhile read for anyone who is interested in the latest developments in advanced Physics.