My God, lol, I own that book but haven't gotten around to it! Hahaha.
Yeah, Blumhouse has published a fair few horror novels that would be neat as a movie or a maze. David Auerbach, who wrote the creepypasta Penpal all the way back in the day, wrote a novel for Blumhouse called "Bad Man" that was very, very creepy at points, think Amityville crossed with Prisoners. I think it stumbled a little at the ending and had one too many red herrings for my taste, and the characters were a little thin, but it's got a very solid core plot and I'd love to see it brought to film and maybe HHN.
EDIT: They never did a Scooby Doo halloween event for the regular daytime park, have they? That seems like it'd be a fun thing to do, just a show or two.