Few large textbooks focus on a single specific sleep symptom. With Sleepiness: Causes, Consequences and Treatment, 2 well-recognized sleep experts, Michael J. Thorpy and Michel Billiard, succeed in producing a textbook that will interest not only sleep specialists and other physicians but anyone interested in the effects of sleepiness, such as those in public health, the medical-legal arena, and occupational health. As Roth states in the foreword, “Excessive sleepiness is used to describe a biological drive for sleep whose intensity is such that there is an inability to stay awake with a high propensity of falling asleep. Excessive sleepiness affects daily living and can be harmful to the individual.” In the Western 24-hour society, where caffeine is used by 80% to 90% of adult individuals regularly, wakefulness, sleepiness, and excessive sleepiness are such an integral part of life that every medical practitioner has to be familiar with the assessment and treatment of sleepiness, as well as its relationship with underlying disorders.