Characters: 8/10
Look, if you're going to throw a bunch of scientists and specialists onto a doomed mission, at least make them interesting—and thankfully, this book delivers. Victoria Stewart is driven, Theo Blackwell is delightfully eccentric, and even the side characters have enough personality to feel like more than just disposable horror movie extras. That said, a few of them fade into the background more than they should, making it hard to care when things go sideways. Still, overall, their motivations feel genuine, and I found myself invested in who would make it out alive (spoiler: not everyone).

Atmosphere/Setting: 9/10
Mira Grant took one look at the Mariana Trench and said, "Let's make this a nightmare." And she succeeded. The research vessel feels claustrophobic, the deep-sea setting is equal parts awe-inspiring and terrifying, and the mermaids? Yeah, they're not here to sing ballads. The horror is grounded in enough realism that it seeps into your bones, making you question why anyone thought this expedition was a good idea. The tension in the action sequences is practically tangible—I could almost hear the distant sound of impending doom.

Writing Style: 9/10
Grant’s writing is a smooth ride: just the right amount of technical detail to make the science believable, but not so much that you feel like you're trapped in a textbook. She knows how to pace the tension and drop just enough exposition without derailing the plot. The dialogue actually sounds like real people talking (a shocker, I know), and the horror elements blend seamlessly with the narrative. Honestly, if she wrote a grocery list, I'd probably read it.

Plot: 8/10
Ah, yes, the classic “let’s investigate a doomed mystery and act shocked when things go horribly wrong” setup. But to its credit, the story is a fun ride. The mystery of the killer mermaids is gripping, the twists mostly land, and the horror is satisfying. A few moments drag a little—like someone let go of the fast-forward button—but the payoff is worth it. It doesn’t completely reinvent the genre, but it does a damn good job playing in the sandbox.

Intrigue: 9/10
From page one, this book had its hooks in me (pun fully intended). The combination of speculative science, horror, and high-stakes survival makes it a binge-worthy read. The suspense builds at just the right pace, and I genuinely wanted to know who (if anyone) would make it out alive. It’s one of those books where you tell yourself, “Just one more chapter,” and suddenly it’s 3 AM.

Logic/Relationships: 8/10
For the most part, the characters make rational(ish) decisions, considering they’re in a horror novel where logic often takes a backseat. The science is handled well enough that it feels believable, and the relationships between characters develop naturally. That said, there are a couple of moments where I had to suspend my disbelief harder than I expected, but nothing too immersion-breaking. The world-building does a solid job of explaining the mermaids without over-explaining, though a bit more depth wouldn’t have hurt.

Enjoyment: 9/10
Was it perfect? No. Did I love it anyway? Absolutely. Between the creepy setting, the tension-fueled action, and the sheer entertainment of deep-sea murder mermaids, this book was a blast. It’s the kind of horror that lingers—not just in your mind but in the part of your brain that will now forever side-eye the ocean. Highly recommend if you want a mix of terror, science, and the gnawing realization that we should probably just leave the deep sea alone.