I'm by no means the best at this but here it goes.
I read the first chapter so far, it's really good, though for formatting on this website I've found uploading in smaller chucks makes it easier for an audience to digest. You don't necessarily have to do this, it's just what I've noticed with my readers. Might give you better luck and more frequent uploads as well.
I'd be a bit careful using historical figures (ya boy H.P. to be specific) just because people will go in already having an idea of that person based on their own knowledge and perceptions. For example, Lovecraft was extraordinarily racist, even for his time. This might effect your foreshadowing as well depending on how much of his life and works you use. People might see things coming. Just make sure you've done your research, even with this being a fictional piece. Also be careful not to pull too much inspiration from Lovecraft's works. Make sure you make it your own, ya know.
I didn't know they were on a boat until the end of the chapter. It does mention a river, but I didn't automatically think boat. I though they were maybe on a train next to the river or something. This should be a pretty easy fix.
Your mood/tone so far is very starchy and brooding, almost Victorian or Edwardian in a seance. This seems to be what you're going for, so that's a good thing! The starchiness is coming specifically from your main character since that's his professional type personality.
Your writing style is strong, and it fits your theme. I've recently switched to third person myself, so I can't really make much of a comment on that stuff yet. If anything I'd say don't be afraid to add more character to your style.
Hope this helps a bit