An interesting and accessible account of a physical theory which dominated the 20th century. The book skilfully guides the reader through the subtleties that mark the historical developments of quantum theory. Adhering to the dictum that `every extra equation, halves sales', much of the technical detail is explained via the use of diagrams. A pity therefore that this approach was not used on pages 14 & 15, where some simple energy diagrams (showing rearrangements of a small assembly of oscillators), may have avoided misunderstanding. Consequently, the explanation of Planck and Boltzmann's reasoning is confusing, as is the distinction between the statistical thermodynamics of classical and quantum particles. With indistinguishable quanta such as photons, we count the number of allowable combinations, whereas for the distinguishable molecules of Boltzmann, we also have to consider permutations of each of these combinations (there are therefore more `fine grained' microstates). Unlike Boltzmann, Planck introduced quantized oscillators but they were still distinguishable, while the much later Bose/Fermi statistics introduced the notion of indistinguishable particle states. [A more pictorial approach to this subjects can be found for example on lulu.com/"Quantum Theory: A concise guide for beginners"]
As well as discussing the various important landmarks in the understanding of quantum theory, the book also contains much detail upon developments in high energy particle physics, as well as cosmology. Overall a very good popular science book, which reveals the somewhat tortuous route to our current understanding of the microcosm and honours the remarkable men who contributed to it.