This is the second edition of a book that has already been well received as a clear and readable introduction to particle physics. It bridges the gap between traditional textbooks on the subject and the popular accounts which assume little or no background in the physical sciences on the part of the reader. The first edition has been carefully revised throughout to provide an up-to-date and comprehensive overview of this fascinating subject. There are also four completely new chapters covering quantum gravity, super-unification, the relationship between particle physics and cosmology, and superstrings. Historical developments are discussed, together with the most important recent experiments, and the theoretical development of the subject is traced from its foundations in relativity and quantum mechanics through to the very latest theories. The book is intended for anyone with a background in the physical sciences who wishes to learn about particle physics. It will also be of value to students of physics wishing to gain an introductory overview of the subject before getting down to the details of the formalism.