The modern world is dominated by flat surfaces. We write, print and project on flat paper or flat screens, which we stare at all day. We inhabit spaces constructed from flat materials. We play sport on level fields. Engineered planar surfaces have become so pervasive and fundamental to behaviour and thought that we barely notice their existence. But flat landscapes are also often disparaged, viewed as featureless, empty and monotonous. Metaphorically, to 'feel flat' is to be bored, dull, lacking energy or inspiration. So what is it about flatness that makes it so desirable and practical in everyday life, yet so unattractive in landscape and as an idea? How has the construction of flat surfaces contributed to a degradation of visual diversity? Flatness attacks these questions by looking first at the ways humans have perceived the natural world around them, from Flat Earth theories to abstract geometric concepts and the Flatness Problem in modern cosmology. It also traces the long historical trajectory of flatness as an engineering ideal, and the representation of the concept in art, music and literature. Flatness is a truly original study, drawing together many strands of thought and practice, from the everyday to the most profound, as it builds a new way of understanding the platform on which the drama of modern life has been played out. Written with wit and wisdom, and splendidly illustrated throughout, the book will appeal to all who are interested in the topography of the modern world.