There is a 600-year-old and 240-paged-book called the Voynich Manuscript, written in a language that’s still completely unknown today.
The Voynich manuscript, often called the world’s most mysterious book, consists of some 240 pages of cryptic text written in an intricate, unknown language, accompanied by strange diagrams and illustrations. It even has fold-out pages, which is pretty nifty for a medieval tome dated to the early 15th century.