Book excerpt: Most of the solar system is in the plasma state and its subtle non-linear interaction with the magnetic field is described for many purposes by the equations of magnetohydrodynamics (MHD). Over the past few years this important and complex field has become one of the most actively pursued areas of research, with increasingly diverse applications in geophysics, space physics and astrophysics. This book examines the basic MHD topics, such as equilibria, waves, instabilities and reconnection and examines each in the context of different areas that utilize MHD. Many of the world's leading experts have contributed to this volume, which has been edited by two of the key enthusiasts. It is hoped that it can help the reader to appreciate and understand the common threads between the different branches of magnetohydrodynamics. This book will be a timely exposition of recent advances made in the field.