Superstrings and M-theory: provocative and controversial, but unarguably one of the most interesting and active areas of research in current physics. Called by some, "the theory of everything," superstrings may solve a problem that has eluded physicists for the past 50 years, the final unification of the two great theories of the twentieth century, general relativity and quantum field theory. Now, here is a thoroughly revised, second edition of a course-tested comprehensive introductory graduate text on superstrings which stresses the most current areas of interest, not covered in other presentations, including: · Four-dimensional superstrings · Kac-Moody algebras · Teichmüller spaces and Calabi-Yau manifolds · M-theory Membranes and D-branes · Duality and BPS relations · Matrix models The book begins with a simple discussion of point particle theory, and uses Feynman path integrals to unify the presentation of superstrings. It has been updated throughout, and three new chapters on M-theory have been added. Prerequisites are an acquaintance with quantum mechanics and relativity.