That was incredibly unsettling. It's a really slow burn, think old school horror, and aside from being The Shining meets The Abyss there's a lot of The Thing here too. Honestly I found parts of the book slow and confusing but that's part of the whole thing. I really want to give this another read if only to try and draw firm lines between what was flashbacks, what was real, and what was hallucination. Try being the operative word here.
It's creepy, disturbing, and can get quite graphic so this book is definitely not for the squeemish but if your stomach (or your mind) can handle it I highly recommend it. Just stick with it to the end, no matter how little sense it's making.