This weekend is the Frankfurt Buchmesse, or book fair. It's a huge, internationally recognized book fair. In fact, I remember reading about it while I was living in the US. It's big and included on the list with the New York book fair.
Here is the website with more information, in English: www.buchmesse.de/en/
That's it for what I'm going to write now, but I'll definitely have more to say about it after the visit!