I quite liked the first book. This one was a bit more of a struggle for me, and it's set up to be open-ended, so there may be a third?
My biggest complaint was that it took until 40% of the book for Avery to go, "Gosh, I think something supernatural is happening." Girl. You JUST went through a crazy supernatural experience. Why are you dragging your heels on this? Even when she figured out that something was going on, she didn't do much about it for quite a while.
Don't get me wrong, there were some really creepy/cool scenes in here, and I think those creepy scenes on their own were more effective than in the first book. Unfortunately, this book felt like it had more plot armor, and the mechanics didn't make sense. I don't want to give spoilers, but as we learn more about that the Black Water is up to in this installment, I kept going, "What, if THAT's true, then how does THIS work?" There were also quite a few scenes were things would work out for the characters in ways that kept the story moving, but that didn't make sense with the plot.
Overall, this book was a bit of a roller coaster for me, and I wanted more coherence from the overall concept. There were some real R.L. Stine moments in here that left me scratching my head as to why they were included, when time could have been better spent fleshing out the narrative.