What are the Paranet Papers?
This is all what I've understood it to be, nothing I'm 100% sure of.
The Paranet Papers are
a number of smaller updates a book* updating the setting part of the game, to "catch up" with later books. The printed books include information up to and including Small Favor, but the books after that show us some fairly cool things with the setting, introduces new weird foes (like the Fomor) and generally shake up the world quite a bit, both on the global and personal scales. The Paranet Papers is supposed to give RPG takes on some of that, and probably expand on some stuff we've found out more about. (I'm thinking that Ghost Story expanded our knowledge of ghosts quite a bit, Cold Days gave us a info on the Sidhe Courts and their Knights aswell as a bit more about Outsiders etc)
*Edit: I had for some reason gotten the idea that it was supposed to be several small publications, like the pre-made stories, but looking at the sneak peeks it seems to be one book which makes a lot more sense.