In April 1958, Yves Klein presented an exhibition in a white room at the Iris Clert gallery in Paris, devoid of all objects save for an empty cabinet. This milestone show, later known as the "exhibition of the void," debuted Klein's "immaterialization of painting": "an ambience, a pictorial climate that is invisible but present." Shortly afterward, Klein upped the stakes even further by offering ritualized sales of "zones of immaterial pictorial sensibility"--i.e., "zones" of nothing--in exchange for a certain weight of fine gold, half of which he then in turn dispatched into the Seine (the other half was used to make gold monochromes). Denys Riout's illustrated study is the first devoted entirely to Klein's immaterial works. Drawing on both known and newly discovered documentation, Riout portrays this development in Klein's thought against its cultural backdrop and attendant postwar philosophic and religious discussions on the idea of the void.