Writer Thomas Chatterton Williams presents his work-in-progress, “Self-Portrait of an Ex-Black Man,” the story of his American family’s multigenerational transformation from what is called “black” to what is assumed to be “white.” He writes about the book: “I’ve spent my whole life believing the American dictum that a single drop of ‘black blood’ makes a person black. Before my daughter, Marlow, was born, in 2013, I’d never remotely questioned the idea. But the shock of Marlow’s appearance exploded such logic in my eyes. Most people will simply call her ‘white.’ And I can’t help but wonder if I’ve nudged my family across an invisible threshold. I chose this admittedly provocative title not because I am no longer black or because my daughter now is white but because these categories cannot adequately capture either of us, or anyone else, for that matter.”