here exists a gap in the present literature on quantum mechanics T and its application to solids. It has been difficult to find an intro- ductory textbook which could take a student from the elementary quan- tum mechanical ideas of the single-particle Schrodinger equations, through the formalism and new physical concepts of many-body theory, to the level where the student would be equipped to read the scientific literature and specialized books on specific topics. The present book, which I believe fills this gap, grew out of two courses which I have given for a number of years at the...