Chance is, you’ve heard of the Voynich manuscript before: a book that was found by book collector Wilfried Woynich in 1912. It is written, by hand, in an unknown language, and according to a letter that – if Voynich is to be believed – accompanied the book, it dates back to some time in the Middle Ages. To date, nobody has come up with a satisfying explanation about who might have been the author, what language it is written in and what the hell its purpose is. Theories are plentiful, but not a single one is really conclusive.
It’s an interesting story and the Skeptical Inquirerhas a great piece on the whole thing (it’s a couple of months old and the translation of a German article that’s even older, but hey, it’s about a book people have been pondering over for a 100 years, so that won’t make much of a difference):
However, the language of the manuscript does not correspond to any European language because the Voynich has no two-letter words or words with more than ten characters. Moreover, it is curious that some words are repeated successively up to five times. The distribution of the letters within each word also does not answer known language patterns. Looking at the text as a whole, far fewer recurring words turn up than would be expected. Such arguments reveal with a high probability that-against all appearance to the contrary-we are not dealing with a simple substitution of letters. There also is no clear evidence that other simple encryption methods were used.
If you want to add your own theory or just make up your mind about the book, you can download the whole script from archive.org.