M. M. Schiffer, the dominant figure in geometric function theory in the second half of the twentieth century, was a mathematician of exceptional breadth, whose work ranged over such areas as univalent functions, conformal mapping, Riemann surfaces, partial differential equations, potential theory, fluid dynamics, and the theory of relativity. He is best remembered for the powerful variational methods he developed and applied to extremal problems in a wide variety of scientific fields. Spanning seven decades, the papers collected in these two volumes represent some of Schiffer's most enduring innovations. Expert commentaries provide valuable background and survey subsequent developments. Also included are a complete bibliography and several appreciations of Schiffer's influence by collaborators and other admirers.