We have added sample dialogue and 4-5 quizzes for each lesson in the paperback books. Also, there are at least two culture blog posts in each book.
The additions to the books are certainly benefits to purchasing the books, but the actual lessons in the books are not that much different than the free PDFs found on TalkToMeInKorean.com. Some of the lessons in the paperback book have been rephrased, rewritten, and proofread to make them easier to understand. :)