Op art got a bad name almost as soon as it got a name. The year was 1964 and Time magazine—or Donald Judd (sources vary)—coined the term to refer to a brand of hard-edged abstract painting that often flirted with optical illusion. At its slickest, op art’s trippy, eye-tickling effects were psychedelic-adjacent, easily transferable to dorm-room posters and throw-pillow fabrics—abstraction’s equivalent to a Happy Meal. But some practitioners probed deeper, finding sublimity in the genre’s rhythmic, sometimes warped geometries, and none more so than Bridget Riley, the 88-year-old English painter who is the subject of a retrospective opening this week at the Hayward Gallery, in London’s Southbank Centre. READ ON

“I sing my sorrow and I paint my joy,” Joni Mitchell said in 2000, nearly 30 years after her manager, Elliot Roberts, and her agent, David Geffen, compiled a collection of her drawings and handwritten lyrics to give to friends at Christmas. “In the early 1970s I used to carry a sketchbook around with me everywhere I went,” she writes in the introduction to Morning Glory on the Vine, the 1971 Christmas present that Mitchell has finally decided to publish, with Houghton Mifflin Harcourt, on the occasion of her 75th-birthday year. READ ON