Safe in a museum vault in Mexico City sits a mysterious book that has been the source of controversy for decades. Known as the Grolier Codex, the book was discovered by looters in a Mexican cave in 1965. They claimed it dated back hundreds of years to the time of the Maya people, but many experts said it was a fake. Now, after half a century, researchers have determined that the text is not only the real deal, it’s also the oldest book ever found in the Americas.