I could be (and most likely am) just grasping at straws with this, but I was getting a major Persona 4 vibe from the last 1/4 or so of that book. I first noticed it when Beth and Norman were convinced that the other person's dark unconscious mind was creating all the crazy sea life and crew members and everything. There are a few points where the conversation mirrors Persona 4's "That's not me" scenes.
By the end, I was thinking of Norman, Beth, and Harry as the founding members of P4's Investigation Team. The giant squid that kept attacking the facility may as well have been named Jiraiya.
I even made a stupid Photoshop picture illustrating my theory, because I guess I have too much free time.