This book is a unique and comprehensive collection of pioneering contributions to the mechanics of crystals by J L Ericksen, a prominent and leading contributor to the study of the mechanics and mathematics of crystalline solids over the past 35 years. It presents a splendid corpus of research papers that cover areas on crystal symmetry, constitutive equations, defects and phase transitions - all topics of current importance to a broad group of workers in the field. The volume thus provides in one place material that is frequently referenced by numerous researchers on crystals across a spectrum of activities in areas of continuum mechanics, applied mathematics, engineering and materials science. Each group of papers or chapters in the book is preceded by a summary introduction that describes how the papers on that topic fit together, and in which Ericksen sketches the context of each paper and shares with the reader his thinking and insightfulness in writing it. The volume, edited by internationally renowned scholars whose works in finite elasticity and continuum mechanics have appeared in a variety of books and prestigious journals published over the past four decades, also includes a very interesting brief autobiography by Ericksen. In it he describes his early life in Oregon, his wartime experiences, his student days and postgraduate study, his introduction to scientific work, and what motivated him in his research. An English translation and revision of the first paper in this volume, originally published in Russian, appears here for the first time.