The introduction of quantum field theory methods has led to a kind of ‘revolution’ in condensed matter theory, resulting in the increased importance of Feynman diagrams or diagram technique. So, it has now become imperative for professionals in condensed matter theory to have a thorough knowledge of this method.The book is intended to teach students, postdocs and young theorists to use diagrammatic quantum field theory methods applied to different problems of modern condensed matter theory, using specific examples of such problems. This latest edition is extended by the inclusion of some new material on superconductivity and diagram combinatorics.