Passing Strange is a nonfiction book by historian Martha A. Sandweiss, published in 2009. The book tells the story of Clarence King, a prominent white geologist and explorer in the late 19th century, who lived a double life as a black man named James Todd. Through extensive research and analysis of King's letters, diaries, and other historical records, Sandweiss reconstructs the complex and fascinating story of King's racial passing and the implications of his actions for both himself and the broader society of the time. The book explores themes of identity, race, and social mobility in the late 19th and early 20th centuries, as well as the ways in which individuals have navigated and challenged societal norms and expectations. Sandweiss's meticulous research and engaging storytelling make Passing Strange a thought-provoking and illuminating exploration of a little-known chapter in American history.