Book excerpt: Since its inception 50 years ago, electron paramagnetic resonance (EPR, also called ESR or EMR) has become a major tool in diverse fields ranging from biology and chemistry to solid state physics and materials science. This important book includes personal descriptions of early experiments by pioneers who laid the foundations for the field, perspectives on the state of the art, and glimpses of future opportunities. It presents a broad view of the foundations of EPR and its applications, and will therefore appeal to scientists in many fields. Even the expert will find here history not previously recorded and provocative views of future directions.