This book is an introduction to the physics of highly excited, easily perturbed or interacting atoms. The book begins with a brief introduction to the traditional view of electron shells and their properties, and then goes on to discuss Rydberg states, quantum defect theory, atomic f-values, centrifugal barrier effects, autoionisation, inner shell and double excitation spectra, K-matrix theory, atoms in high laser fields, statistical methods, quantum chaos, and atomic effects in solids.  Meer