At 18, Corita Kent (1918-86) entered the Roman Catholic order of Sisters of the Immaculate Heart of Mary in Los Angeles, where she taught art and eventually ran the art department. After more than 30 years, at the end of the 1960s, she left the order to devote herself to making her own work. Over a 35-year career she made watercolors, posters, books and banners--and most of all, serigraphs--in an accessible and dynamic style that appropriated techniques from advertising, consumerism and graffiti. The earliest, which she began showing in 1951, borrowed phrases and depicted images from the...