I'm hopeful that we will be hearing more about Mach's Principle in the future. Modern Physics may provide the theoretical underpinings that eluded Mach and his contemporaries. It was fascinating to learn just how sketchy Mach's contribution's were- and that the development of a theory of inertia were instead made by Mach's colleges. My only regrets were that the work of Dennis Sciama and Roger Penrose were not included. This book illuminates a topic in physics that is controversial, problematic, and very interesting.