This work, written in a particularly readable and accessible style, stresses the fundamental ideas relevant to the understanding of the electrical properties of materials. Topics are selected so that the operation of devices having applications (or possible future applications) in engineering can be explained. The mathematical treatment is deliberately kept simple: well within the grasp of a second-year student. This is achieved by choosing the simplest model that can display the essential properties of a phenomenon and then examining the difference between the ideal and the actual behavior. For this new edition new or updated information will be found on Fullerenes; III-V and II-VI semiconductors; High Electron Mobility Transistors (HEMTs): Photorefractive materials and semiconductor lasers; Optical fibre innovations; New magnetic materials; the Quantum Hall effect; and many other topics. This text remains a highly readable, comprehensive, and straightforward introduction to the electrical properties of materials.