An irascible, brilliant man, trained as an economist, Karl Helfferich became one of Wilhelmine Germany's leading financiers in the years after 1905. During World War I, he held a series of important Reich offices and, after 1918, became a leading right-wing politician in the Weimar Republic. As creator of the basic plan to stabilize the mark in 1923, he played a major role in ending the catastrophic postwar inflation. John Williamson's biography of...