With at least a half dozen hydrogeochemistry textbooks on the market, why do we need another one? Aqueous Environmental Geochemistry provides an answer to that question. Most current texts fall into one of two categories. Some are heavy on basic concepts and physical chemistry fundamentals, but contain relatively few relevant examples from the natural environment. Other texts fall at the opposite end of the spectrum, with plenty of good geochemical examples but only qualitative or semiquantitative approaches to understanding them. In contrast, Donald Langmuir's new book provides a thorough development of fundamentals important in low temperature aqueous geochemistry, along with a wealth of examples to illustrate how these fundamentals are applied in solving real problems.