The past five years have seen the publication of several books on amyotrophic lateral sclerosis (ALS). Why another one now? Several answers are evident. Some of the previous books were focused on clinical management, or diagnosis, or pathology. None has been as comprehensive as this volume of Professor Eisen and his colleague Dr Krieger. The writing here is seamless, in contrast to multi-authored books. The range of subjects covered is astonishing, especially for a veteran like me. I can remember when there was almost no research on ALS, because there was not much to do except for clinico-pathological correlations. This book, however, considers the whole range in depth from epidemiology to clinical features. Why the predominance in men? How does age at onset or family history affect prognosis? What accounts for clusters? What is the current interpretation of the high incidence on Guam? The differential diagnosis is discussed in detail, including a judicious presentation of motoneuropathy. The authors also provide a full description of cellular pathology and theories of pathogenesis, including inherited human and mouse diseases, and transgenic murine models. Questions are raised and answered about the significance of ubiquitination, Bunina bodies, Lewy bodies, and neurofilaments. Apoptosis is explained. In a detailed discussion of pathogenesis, the authors consider the exci to toxic theory of pathogenesis, which they favour, and the autoimmune theory, which they find wanting. Naturally, electrophysiology gets full treatment, including the authors' theory that the disease begins in the upper motoneuron rather than in both upper and lower motoneurons simultaneously.