This book shows just how tortuous has been the struggle in physics (and science in general) to arrive at and comprehend its fundamental concepts. The very first paragraph in Einstein's foreword is worth the price of the entire book, if one truly understands what Einstein has said. Most of us came into physics via ordinary textbook courses, where unfortunately most of the approach was to quickly master the equations and their methods of application. Somehow we never understood that the very foundations of physics are still very much at issue, and our teachers either did not realize this themselves, or considered such musings trivial, or were just too busy to enlighten us. Most of us think that things like space, mass, time, charge, field, potential, zero, and unity are obvious, and it can come as a major shock to one's system to find out that they are not. Most such fundamental concepts still do not have a satisfactory definition. Jammer's book, while cumbersome by its very scholarship, does give one a grasp of just how difficult the foundations problems -- such as the nature of space -- really are. If one is seriously interested in this sort of "deep" problem, then one must discover the literature oneself. Jammer's book is a must. I gave the book a 9 instead of a 10 because of its overall ponderous nature, but highly recommend it to anyone who is deeply interested in the foundations concepts of physics, how we got where we are, what we did along the way, what we may have yet missed, and just how firm or shaky are our concepts today. We also recommend Jammer's other studies of the concept of force and the concept of mass.
A very deep book, filled with excerpts in native languages from ancient Greek to modern German, French, and Russian, and with tensor mathematics and other such nonsense. If you want to have your concept of space and time ripped out from under you and your horizons dramatically broadened, check this one out! (BTW, I gave this a 9 instead of a 10 solely because of the weightiness of the material.)