An entertaining albeit at times rather academic discussion of what research has uncovered about the nature of sleep and sleep disorders. Lavie, a sleep researcher and dean of the Faculty of Medicine at the Technion--Israel Institute of Technology, is clearly enthralled with his subject, and his enthusiasm shines through the sometimes stilted presentation. The author gives a brief history of the young field of sleep research--the first sleep recordings of brain-wave activity were conducted at Harvard in 1935, and the discovery of REM (rapid eye movement) sleep, the sleep of dreaming, was not made until 1953--describes what goes on in a sleep laboratory and outlines what science has learned about biological clocks, dreams, the sleep of animals, and sleep deprivation. Memorable facts emerge: The dolphin, it seems, sleeps with half its brain awake, and humans can go without food longer than without sleep. In the second half of the book Lavie concentrates on sleep disorders and their treatment. His discussion of insomnia includes a fascinating account of research conducted in Haifa during the Gulf War, which concluded that while people were afraid to go to sleep for fear of missing the warning alarm of a Scud missile attack, once they fell asleep, they slept normally. Lavie describes the use of phototherapy, or light therapy, in the treatment of jet lag and sleep timing disorders; mechanical solutions to the problems of sleep apnea, in which the sleeper stops breathing; and the strange malady of narcolepsy, which is marked by sudden, uncontrollable attacks of daytime sleep. For parents, there are explanations of children's sleep patterns and advice on dealing with their sleep problems, and for the elderly, there are cruel truths about the fragility of sleep in old age. An eye-opening trip through the land of sleep by a thoroughly professional guide.