The Casimir effect arises when the zero-point vacuum oscillation spectrum is distorted by boundedness of the field quantization domain or by non-trivial spatial topology. As such, it is a widely used and intensely discussed phenomenon. This is the first book devoted to the Casimir effect. It will be valued by workers in a number of fields, including elementary particle physics, statistical physics, quantum field theory, gravitation and cosmology. Methods of calculating Casimir energies and forces are considered, and results given for bounded domains, dispersive media, and topologically non-trivial spaces. All these applications are outlined in this work covering a widely known, used and intensively discussed effect by specialists.