The author who has sold the most books to date is difficult to determine precisely due to varying sources and estimation methods. However, some authors are widely recognized for their immense commercial success. J.K. Rowling, the author of the Harry Potter series, is often cited as one of the best-selling authors of all time, with hundreds of millions of copies sold worldwide. Other authors who have achieved significant sales include Agatha Christie, William Shakespeare, Dan Brown, and Stephen King.