This book is about the underlying principles of symmetry, thermodynamics and electronic structure that pertain to crystalline solids. After years of teaching graduate students in the areas covered, the author has a good idea of what major notions of group theory and thermodynamics are useful to students of solid state chemistry, and of what fundamental concepts are necessary for a clear understanding. Thus the book deals with lattice symmetry, space groups, reciprocal space, Landau theory, X-ray diffraction, heterogeneous equilibria and simple band theory, in a rigorous and thorough treatment.