Available in paperback for the first time, this book describes the main methods of one- and two-dimensional high-resolution NMR spectroscopy in liquids within the quantum-mechanical formalism of the density matrix. In view of the increasing importance of NMR in chemistry and biochemistry, it is particularly addressed to those scientists who do not have a working knowledge of quantum calculations. This knowledge is provided in the first part of the book through a description of quantum mechanics as applied to spin systems: this description is both self-contained and limited to the essentials. A final chapter is devoted to the principles of relaxation theory.The book will endow the reader with enough practice in the theoretical tools of NMR to enable him to analyse critically comprehensive treatises or articles on new methods.