
I've been fascinated by this thing ever since I came across it on a cracked.com article.
Basic overview:
It's an early 15th century handwritten codex written in a lanuage indecipherable even to this day. Many cryptologists and linguists have tried to understand the words in this manuscript with no avail. The manuscript is known for it's weird, sometimes creepy illustrations of unidentifiable plants and odd. . .rituals? If you could even call them rituals. Just all around head-scratching stuff. You can read more on the wiki page here.
I really want to one day see this book for myself. Lucky enough, the closest thing I'll get is THE ENTIRE COPY ONLINE.
SO COOL.
One of my crazier theories is that this is a book from an alternate Earth.