This second edition of the well-known work stresses important aspects of magnetic resonance theory that are of increasing importance to the research worker. Presents mathematical background and the basic prototype two-spin 1/2-1/2 Hamiltonian treatment as a building block to the more specialized subjects developed: higher spins and anistropies, applications to atomic spectra, crystal field theory, Mossbauer resonance, types of double resonance, and dynamic polarization. Specialized extensions are then discussed at length, with the advantage of showing clearly their relationships to the main body of magnetic resonance theory: ENDOR, ELDOR, polarization, spin labels, saturation transfer and fourier transform methods, and NMR imaging. Much of this material is treated by means of the uniform formalism based on the direct product matrix expansion technique.