"In keeping with the purview of the Structure and Bonding series, this volume is a critical review of magnetic funtions and the methodologies associated with calculation magnetic parameters, modeling magnetization, and predicting magnetic susceptibility. This topic is particularly timely, as a wide array of emerging technological applications are dependent upon magnetic behavior (including magneto-caloric materials and magneto-optical information storage devices), and spin-based spectroscopy (e.g. ESR) continues to help elucidate biological reaction mechanisms and characterize the structure and bonding of novel compounds."