Self-organized criticality (SOC) is based upon the idea that complex behavior can develop spontaneously in certain many-body systems whose dynamics vary abruptly. Researchers have observed characteristic general behavior in systems as diverse as earthquakes, sandpiles, and even biological evolution, and have suggested SOC as a way of understanding this behavior. This book is a clear and concise introduction to the field of self-organized criticality and contains an overview of the main research results.