Biography of X is a 2023 alternative history novel by American writer Catherine Lacey published by Farrar, Straus and Giroux. The novel purports to be a 2005 biography of the musician and artist X, written by her widow, C.M. Lucca, as a response to an unauthorized and apparently inaccurate biography of her wife written after her death. The novel takes place in an alternate timeline in which the Southern states of the United States seceded in 1945 after building a wall segregating them from the rest of the country. Catherine Lacey (born April 9, 1985) is an American writer. Lacey's first novel, Nobody Is Ever Missing, was published by Farrar, Straus and Giroux. Dwight Garner, in The New York Times, called her prose "dreamy and fierce at the same time." Time Out named it "the (hands down) best book of the year. It also made The New Yorker's list for the best books of 2014. It has been translated into Dutch, Spanish, Italian, French, and German. The novel was a finalist for the New York Public Library's Young Lions Fiction Award. In 2016, Lacey won a Whiting Award for her fiction.