As other reviewers have noted, this book contains very little useful discussion to probe the meaning of the equations described. It is profusely wordy without making any useful contribution to the reader's understanding of the connection between the mathematics and the world(s) it describes.
Other reviewers have also noted the author's rather short-sighted critique of Maxwell's original form for the equations of electro-magnetism in favour of Heavyside's representation. This is an unfortunate and surprising feature of a book written by an historian of science who must surely be aware that all major physical theories are expressible in a variety of mathematical forms (Wave mechanics or Matrix mechanics, Newton's equations or the Maupertuis/Hamilton Principle of Least Action, QED Feynman diagrams or Schwinger/Tomonaga integrals, etc etc etc). A real beauty of Maxwell's electromagnetism is that the existence of the magneto- part follows directly and inevitably from the elctro- part *given* the principle of relativity. That is less than obvious from either Maxwell's or Heavyside's formulation of the equations, was perfectly understood by Einstein, but was made most clear by Herman Weyl who (in effect) re-wrote the equations in frame invariant Tensor form, thus proving them to obey the General Principle of Relativity. Space, Time, Matter (Dover Books on Physics)
Ian Stewart's book Seventeen Equations that Changed the World is far better in both quality and precison of writing and in modern relevance of the material chosen. Stewart also manages to find worthy candidates more recent than 1927 - which is where the present author runs out of ideas, with Schrodinger's equation and Heisenberg's 'Uncertainty principle'. As all serious quantum physicists of the time, including Schrodinger himself, would have agreed, the 'Schrodinger Equation' was not consistent with the Special Theory of Relativity and, therefore, could not be regarded as the final answer. But within a couple of years Dirac had produced his equation for the relativistic electron field ... from which followed the revolutionary concept of anti-matter and most of modern Quantum Field Theory. To quote Werner Heisenberg " [Dirac's] discovery of anti-matter was perhaps the biggest jump of all the big jumps in physics of our [20th] century. It was a discovery of utmost importance because it changed our whole picture of matter". The lack of Dirac's equation in this role-call of 'Great Equations' is just the first of several that were missed by Robert Crease.