I ran this during a rare RPG weekend with four good friends, and had a blast.
It's a great setting, there's room for some truly horrific roleplaying moments and some pretty grueling player vs. player stand-offs.
But as a product, it's honestly pretty sketchy. I'd skimmed it ahead of time, but wasn't counting on running it. A few hours beforehand I changed my mind and read it through 3-4 times, making notes as I went along, but by the time we started I still wasn't sure there was a game there.
The sequence of events that've lead up to the scenario are sketchy, the use of the Man in Black and his role as a Germanic folklore figure are left largely untouched and the King in Yellow, which I haven't read, isn't summarized in any way. The player characters aren't ready for play, missing combat skills (and they'll be needed I can assure you) and either miss important pieces of information or simply don't have enough. This is really more of a draft or a set of expanded notes.
I'm giving it 4, because we had a lot of fun with the sandbox setting and I would run it again in the blink of an eye. That said, next time I'll have to spend a few days preparing to iron out the inconsistencies.