Last June, Britain voted to leave the EU, and just a few months later, Ali Smith released her new book, “Autumn,” which is being heralded as the first great post-Brexit novel. The book starts off her planned quartet of novels about the seasons, and while it feels allegorical, it’s also firmly grounded in current events. “I kind of felt I would be cheating the novel if it didn’t face the contemporary or the contemporary didn’t face it,” Smith says.