The author Esmeralda Santiago has been writing about Puerto Rico and questions of immigration and identity since the early nineties. But, in 2008, she suffered a stroke that left her unable to decipher words on a page. In the months that followed, she relied on some of the same strategies she’d used to teach herself English after moving to the United States as a young teen-ager—checking out children’s books from the library, for example, to learn basic vocabulary. Santiago’s latest book, “Las Madres,” includes a character named Luz who goes through a similar experience after a traumatic brain injury. “That sense stayed with me long after I was over that situation—that feeling between knowledge and ignorance,” she tells the staff writer Vinson Cunningham. “For me, Luz is almost representative of Puerto Rico itself. We have this very long history that we don’t necessarily have access to. . . . Those of us who live outside of the island, we live the history but we don’t really know it.”