Book excerpt: The purpose of this book is two fold. First to explain the properties of low dimensional solids such as electronic, vibrational and magnetic structure in terms of simple models. These are used to account for the properties of three dimensional materials providing an elementary introduction to the physics of low dimensional materials. The second objective is to discuss the properties of newer low dimensional materials not made of carbon. These are now the subject of research and describe various phenomena in them such magnetism and superconductivity.