There is a growing body of scientific knowledge regarding development during the middle years which has so far been relegated to discipline-specific texts and journals (e.g., clinical psychology and endocrinology).

Life in the Middle consolidates main findings across disciplines, with a life-span perspective regarding mid-life. Coverage includes individual development in middle age from the psychological and biological perspectives as well as the sociocultural context in which middle-aged individuals live and work, including physical health in mid-life, psychological well-being, cognitive development, the impact of work on the individual, and the general development of the "self." This age period is increasingly becoming the focus of scholarly attention as the largest cohort in U.S. history are now moving into the middle years (e.g., the "babyboomers"). From 1990 to 2015 the number of middle-aged people will increase 72 percent from 47 to 80 million.