This is the second edition of a well-received book that is a modern, self-contained introduction to the theory of gravitational interactions. The new edition includes more details on gravitational waves of cosmological origin, the so-called brane world scenario, and gravitational time-delay effects.The first part of the book follows the traditional presentation of
general relativity as a geometric theory of the macroscopic gravitational
field, while the second, more advanced part discusses the deep analogies (and
differences) between a geometric theory of gravity and the gauge theories of
the other fundamental interactions. This fills a gap within the traditional
approach to general relativity which usually leaves students puzzled about the
role of gravity. The required notions of differential geometry are reduced to
the minimum, allowing room for aspects of gravitational physics of current
phenomenological and theoretical interest, such as the properties of
gravitational waves, the gravitational interactions of spinors, and the
supersymmetric and higher-dimensional generalization of the Einstein equations. This textbook is primarily intended for students pursuing a theoretical or astroparticle curriculum but is also relevant for PhD  students and young researchers.