Huge news from the book world today: Harper Lee has announced she’ll publish a sequel to her classic novel To Kill a Mockingbird. It’s called Go Set a Watchman, and it comes out July 14th. Lee is 88 years old. She never published another novel after Mockingbird, which has sold more than 40 million copies and has been translated into more than 40 languages. What’s the new book about, and why now?