Roger Elliott has been one of the leading figures in theoretical condensed matter physics for over three decades. In 1989, a Symposium was held in Oxford to mark his sixtieth birthday. This book is a collection of 38 articles by his colleagues and ex-students, which are based on papers presented at the Symposium. The articles are authoritative accounts of current developments in the physics of random systems (structural, dynamic, and statistical properties), magnetism and superconductivity, phase transitions, and quantum optics and excitonic effects. The theme of disorder is one that runs strongly throughout the book.