I want to know the answer to the following question:
How many copies of the book have been sold?
All the background I'm provided with is that "A 1991 survey by the Book of the Month Club and the Library of Congress Center for the Book found that To Kill a Mockingbird was rated behind only the Bible in books that are "most often cited as making a difference".[note 1] It is considered by some to be the Great American Novel.". Is that enough to answer the question?