Optical Interactions in Solids presents an extensive and unified treatment of the basic principles of the optical properties of solids. It provides a theoretical background to workers in the field of laser physics and absorption and fluorescence spectroscopy of solid state materials. The book is a comprehensive coverage of the subject and is systematically and didactically organized. The level of presentation is such that it will benefit and interest both advanced students and research workers. Group theory — which is useful throughout — is introduced early in the book advocating the scientific community to overcome the reluctance to employ this powerful method. Consistent emphasis is given throughout the book to the relevance of symmetry and to detailed calculations. Different subjects as various as quantum theory of radiation field, thermal vibrations of molecules and crystals, and covalent bonding are brought together in a unified treatment which requires knowledge of all these topics and this points to the interpretation of the spectral properties of solids. The content of this work could be used as a two-term graduate course in solid state spectroscopy.