The ten essays Oliver Sacks gathered for this volume shortly before his death might at first seem like a miscellany, the meanderings of an inexhaustibly curious man, interested in everything. But The River of Consciousness (Knopf, $27.95), covering such classic Sacks themes as perception and misperception, memory, time, creativity, and how the abnormal illuminates normality, is a remarkably tight and focused collection. In making this coherence out of many disparate fields—biology, history, biography, medicine, photography—the book mirrors the title essay’s discussion of William James’ theories that the seemingly continuous state of consciousness is composed of innumerable discrete moments. James, one of Sacks’ heroes, returns throughout this book, as do Darwin and Freud. Like Sacks, these thinkers embodied an admirable “spaciousness of mind,” and Sacks profiles not their celebrated achievements but their lesser-known accomplishments in areas outside their specialties. He lays out Freud’s early work in neurology and Darwin’s late work in botany, a field that was mostly descriptive before Darwin’s six books and seventy-plus papers transformed it into an evolutionary science. Sacks also picks up threads from his own prodigious writing, revisiting many of his earlier books to add new information, revise conclusions, and, most of all, to ask more questions.