Colby College English professor and cultural critic Cedric Bryant was still awaiting his preorder of the new Harper Lee novel “Go Set a Watchman,” but he read the first chapter online and enough news accounts to feel certain of one thing: Just as Lee’s “To Kill a Mockingbird” helped guide the national dialogue about race when it was published in 1960, “Go Set a Watchman,” published Tuesday, is certain to be part of the conversation about race in America today. “What little we already know about this book confirms what is a truism about race in our culture, and what we keep learning and relearning, and that is that race matters.