In an 1852 Punch cartoon, a middle-aged man looks in a mirror and says, “Good gracious! Is it possible?—No! Yes! No!—Yes! Yes, by Jupiter, it's a grey hair in my favourite whisker!” Jokes like this might be routine to us, but in Victorian England they represented a new way of thinking about age.Middle age had been considered the prime of life since Aristotle, an idea evident in “steps of life” drawings that were popular from the medieval era into the nineteenth century. They feature a fifty-year-old man—or less commonly a woman—who stands proudly on the top of an arched set of steps depicting the decades of life from ten to ninety. In the eighteenth century, concern about aging remained on the elderly. Longevity texts, describing elaborate techniques and rituals for living into a "green” or healthy old age, became the rage.Though scholars usually discuss midlife anxiety as a product of the twentieth century, I argue that age anxiety was expanded in Victorian Britain to include the middle of the life course. The word “midlife” itself first appeared in an English dictionary in 1895 to designate this developing idea. In Aging By The Book, I demonstrate that concern about midlife became common during the Victorian era, that we inherited our obsession with being “over the hill” from the nineteenth century.