This book on Special Relativity, with unique chapters on the Dirac equation and General Relativity, is especially suitable for a one-semester undergraduate physics course on Special Relativity (with perhaps some coverage of the qualitative features of General Relativity). It can also be used in a combination of undergraduate courses including modern physics, particle physics, optics, and Quantum Mechanics; or in classical mechanics at the physics graduate level. The book also includes coverage of the history of relativity, particularly with respect to developments in electricity and magnetism, particle physics, and cosmology. This is the revised second edition.