This book covers the basics of magnetic quantities and how to measure them, the properties and behavior relevant to magnetic devices, and the materials actually used in practice. It is presented at a practical rather than theoretical level. This allows the reader to develop a real physical understanding of the various quantities involved in magnetism through measurement, which is stressed throughout the book. The book is divided into three distinct sections. The first two chapters introduce the reader to magnetic phenomena, magnetic units and magnetic measurements. Chapters 3 through 10 discuss the basic science of magnetic materials. Using the concepts introduced earlier in the book, the last four chapters discuss specific types of magnetic materials: soft magnetic materials, permanent magnets, recording materials and superconductors.