Where does “The Nocturnal Brain: Tales of Nightmares and Neuroscience,” by British neurologist Guy Leschziner fit within the flurry of recent popularizing books about sleep? I’ve read four such, two of them venturing into self-help territory and one being a memoir about insomnia, but “The Nocturnal Brain” is none of those. Instead, it’s a wise journey through sleep pathologies and problems, and reflections on the nature of sleep itself. He covers delayed sleep phase syndrome (the day/night boundary shifting every day!), sleepwalking (including motorbike driving while asleep!), REM sleep behavior disorder (including sleep-bound violence), “tired all the time,” false accusations of sleep-talking, narcolepsy (falling asleep willy-nilly), restless legs syndrome (I’ve had this, a teeny bit), hallucinations, sexsomnia (guess) . . . I list these because they fascinating array. Leschziner also covers in detail general insomnia, including what is apparently commonplace, people reporting poor sleep but actually sleeping enough hours (I suspect this is me). The author writes extremely smoothly, with great compassion towards his case studies, and the book is a treat to read. Amongst all these observations, Leschziner also muses about the nature of dreaming (which may well underpin the purpose of sleep), and although he does come down in favor of one hypothesis, in the end he concludes that “we have only just scratched the surface.” Highly recommended.