Ten Most Expensive Books for your Reading Pleasure

In my previous postings I have listed ten most expensive photographs, paintings, cars, homes and sculptures. Today I am listing the top ten most expensive books. Before I did my search, My educated guess for number 1 was either the Gutenberg Bible or the Birds of America by Audubon. Again, I was wrong and surprise to read the following list. This shows how ignorant I am about books. So before you open the link below, can you give me your educated guess on the number 1 most expensive book in the world.

http://www.worldstopmost.com/2017-2018-2019-2020/news/most-expensive-books-world-top-10-best-selling-popular-list/