On 4 July 2012, the announcement came that one of the longest-running mysteries in physics had finally been solved: the Higgs boson, the missing piece in understanding why particles have mass. On the rostrum, surrounded by jostling physicists and media, was the particle's retiring namesake - the only person in history to have an existing single particle named for them. Drawing on years of conversations with Higgs and others, Close explores how Higgs became one of the world's most important scientists. Close shows that scientific competition between people, institutions and states played as much of a role in making Higgs famous as Higgs's work itself. 'The Mystery of Mass' is a revelatory study of both a scientist and his era, which challenges and transforms our understanding of modern physics.