What do we mean when we call something “ugly”? Author Gretchen Henderson, an academic now teaching at Georgetown who focuses on the intersection between literature, art, and history, asks this question in her book, Ugliness: A Cultural History. Tracing the evolution of ugliness through the ages and across cultures, Henderson begins in antiquity with the Greeks’ idealized and marbled notions of beauty before detailing Roman Emperor Elagabalus’ pastime of gawking at deformed people during feasts. From medieval gargoyles to grotesque literature’s Frankenstein, Henderson meditates on ugliness as both a physical descriptor and a cultural construct used to capture something degenerate on a moral, ethical, or philosophical level. Sometimes what’s on the outside coheres with the inside (think Cinderella’s stepsisters), sometimes it doesn’t (the Ugly Duckling), and sometimes it’s more complicated—as we see when European art, in the wake of World War I, shifts from realism to surrealism, turning beauty on its head and distorting the human form. Expect Henderson to challenge preconceived notions about this complicated concept. An idea that evades simple definition, ugliness is not simply the antithesis of beauty. There’s something compelling about its layered imperfections and its shifting meaning. Gretchen Henderson reads at 6:30 p.m. at Kramerbooks, 1517 Connecticut Ave. NW. Free. (202) 387-1400. kramers.com.