This book provides a thorough and pedagogical introduction to Einstein's special theory of relativity. It is suitable for anyone with a minimum of one year of university physics with calculus. The text is divided into fundamental and advanced topics. The fundamental section starts with a recalling of the Pythagorean rule and its relation to the geometry of space, and then covers every aspect of special relativity, including the history. The first part of each chapter includes an exercise to stimulate the reader's spatial awareness and geometric thinking. Advanced topics sections start with a treatment of the impact of relativity in quantum theory, with an introduction to relativistic quantum mechanics and quantum field theory. The book also covers the group theory of the Lorentz group, a simple introduction to supersymmetry, and ends with a chapter on cutting-edge topics such as general relativity, the standard model of elementary particles and its extensions, superstring theory, and a survey of important unsolved problems. Each chapter comes with a full set of exercises covering every topic presented and the book is accompanied by an interactive CD-ROM.