This highly regarded and historic book represents the first comprehensive discussion of both theoretical and experimental aspects of molecular magnetism research. It covers basic concepts of magnetisation and magnetic susceptibility, establishes the fundamental equations of molecular magnetism, and examines molecules containing a unique magnetic center. The treatment is suitable for graduate students and professionals in inorganic, theoretical, physical, and bioinorganic chemistry; materials science and molecular electronics; and physics and biophysics. This newly updated edition features contributions from the author's colleagues, including Dr. Michel Verdaguer.