When extra-virgin olive oil arrived in American kitchens around 1980, a set of myths came with it. You can’t use it for everyday cooking. You can’t use it for deep-frying. You must hoard your best stuff and bring it out only for occasional drizzling. Not one of those turns out to be true: Olive oil is an excellent all-purpose cooking oil, but at the time it was too expensive for cooks to use freely. In the meantime, the price has fallen, but global demand has grown far beyond supply, and the entire business has been transformed by technology, global trade and climate change. It has also been wracked by fraud, with millions of consumers around the world regularly paying for “extra-virgin” olive oil that is cut with inferior olive oil, mixed with cheaper oils, or colored with chlorophyll or beta carotene. Labeling has become a minefield, despite efforts by the European Union to enforce rules and make meaningful distinctions among terms like “made in Italy,” “imported from Italy” and “packed in Italy.” The European Union’s system of food certification (appearing as a DOP or PDO seal on a label) is relatively reliable...