We know this much so far about Harper Lee’s new book: Atticus Finch is 72 and suffering from rheumatoid arthritis; Scout is a grown woman who has a suitor most anxious to marry her. “Go Set a Watchman” begins with Scout, otherwise known as Jean Louise Finch, returning by train to Lee’s legendary Maycomb, Alabama, on one of several annual visits she makes from New York, where she is greeted by young Henry Clinton.