Book excerpt: Stable Isotope Geochemistry is an introduction to the use of stable isotopes in the fields of geoscience. It is subdivided into three parts: - theoretical and experimental principles; - fractionation mechanisms of light elements; - the natural variations of geologically important reservoirs. In this updated 4th edition many of the chapters have been expanded, especially those on techniques and environmental aspects. The main focus is on recent results and new developments. For students and scientists alike the book will be a primary reference with regard to how and where stable isotopes can be used to solve geological problems.