Well the overall plot of that episode is a little confusing, especially to someone who isn't a fan of the show. Basically, there's been a whole angels & demons theme going on this season, and then one day Kripke was all, LET'S HAVE A PROPHET. So the boys discover these books that are very obscure and read only by a handful of geeks and they basically tell the story of the last 3 years of their lives-- one horror novel per episode. So they track down the author, and he's been unaware that he's actually a prophet writing down his visions of real people. It's fucking hilarious.

YES, THEY FIND WINCEST.


For the record: I'm a Supernatural fan, but I hate Wincest, and basically don't participate in the fandom at all. Because they are all crazy.