Played about six hours so far, going at a leisurely pace and exploring. So far, I'm fond of the game, it's not perfect but I appreciate the themes and narrative so far, and I actually think the game is scarier than Amnesia for me at least (I didn't find Amnesia that scary, the monsters were too easy to hide from, impossible to run from, and if you died they despawned, which took a lot out of it), but not as scary as Penumbra was for me at times so far at least.
It's very different than Frictional's previous games, it almost doesn't feel like a game made by them except for some specific scenes. I don't say this as a bad thing, but while Penumbra and Amnesia, while different feeling, had things similar enough they were obviously by the same people, this one I wouldn't of guessed were by the same guys if I hadn't known about it or the Frictional Logo was at the start of the game. The design of the game, the puzzles, the enemies, the atmosphere, the story, the setting, just everything feels very different outside of maybe the first monster.
The two best parts for me right now are the story and the monsters. The game's themes, pacing, and characters I'm enjoying a lot right now, though I feel most have touched on this already and there's not much I can add, and need to experience the rest of the narrative obviously. On monsters, I actually think they are Frictional's strongest, they're very varied so far and I think the areas you encounter them in are well-designed for them and memorable, not always scary, but tense (and sometimes scary, I will admit there's a few moments that have gotten me thus far). But I love the monster design, the layout of the encounter areas, and the behaviors and sounds of the monsters themselves. You meet the monsters so infrequently thus far at least, which might actually be kind of nice. I will also throw out there I'm really excited to see what modders can do with their custom campaigns and maps with these monsters, I feel Frictional partially put so much effort in differentiating them so much despite the monsters (so far) not appearing much so they'd be very versatile for custom campaigns to work with. Penumbra had some slight monster differences but mostly samey feeling, while Amnesia's monsters were very samey feeling, so the huge differences between monsters is welcome, even if some wear their inspirations on their sleeves. Encountered four different monsters so far who all behave quite differently.
It's very different from Frictional's other games its a bit hard to compare them, but personally I think I enjoy this more than Amnesia thus far, I actually even like the ocean segments and haven't really gotten lost in them yet (except a small bit in the Delta area). It's a bit below Penumbra for me right now as my favorite Frictional game, but the second half of it could make or break it for me.