The Riemann Legacy Book

A book about the history of the 23 problems which Hilbert listed in his talk at the International Congress of Mathematicians in 1900 as important questions for the mathematicians of the twentieth century. The perspective is wider than if it were about just one problem, but more focused than a comprehensive history of twentieth-century mathematics would be. What I liked best was that even though it mentions mathematicians' personalities, friendships, and rivalries, it only does so it can explain how they affected the development of mathematics, and not the other way round as books on the history of science almost always do. Almost all of the problems are solved now, though some of them aren't simple yes-or-no questions and the Riemann Hypothesis has outlasted the century.