Although sleep research is still in an early phase, enough is known to discard some old theories (the brain shuts down) and document others (one milk ingredient has soporific powers, counting sheep can help). Insomnia has as many variations as patterned sheets: almost everyone endures it occasionally, but for chronic sufferers relief may be available--and not from prescription sedatives. Turbo skims over the common causes of sleeplessness--medical, psychological, situational--characterizes the four stages of sleep, and summarizes lab findings on falling-asleep times, dream interruption effects, marathon wakefulness sessions, etc. Also considered are such now-treatable disorders as narcolepsy, sleep apnea, nocturnal myoclonus (kicking), bruxism (tooth grinding), sleepwalking (an inherited tendency), and sleep talking (""There are enough stairs to make a stick of lemon juice spoil""), plus short sections on sleep patterns, dream content, and dream control. It's too stimulating to make good bedside reading, but the Sominex set can benefit from his systematic uncovering of recent research discoveries.