TL;DR decent game for fans of walking sims or horror games like Amnesia. Amazing atmosphere, voice acting, graphics, world design, but dull gameplay and not much of a horror game. The DLC captures the horror experience better and is also very worth playing.
The biggest thing this game has going for it is the setting, atmosphere, characterisation of the world it builds, which I think has generally been The Chinese Room's strength (see Everybody's Gone to the Rapture as a comparable example in this regard). It is such a distinctive and well-realised setting, enabled and furthered by the beautiful graphics and top-notch voice acting and dialogue.
Having said that, I enjoyed the start of the game the most, when you can really soak up the atmosphere before the story really gets going. IMO it loses a lot of that once it starts tying in more of the horror elements, though it does still maintain a consistent setting and tone throughout.
I also didn't find it to be the most engaging game ever. If you've played other walking sims you probably know what to expect, but there's no inventory or resource management etc., you basically just walk from place to place, crawl across beams, climb up ladders, turn valves, sneak round monsters, etc. It's not boring, but for me the gameplay was just fine, and at times a little janky and irritating, so the short playtime works in its favour I think. It doesn't overstay its welcome too badly. I think a single playthrough of the basegame generally takes people 3-5 hours, but it took me about 8 because I like taking my time and looking at everything etc.
The story is decent, but more serviceable than really profoundly engaging. It kept me engaged enough to want to see how it played out, but it's nothing too special. The biggest question you have through the game remains unresolved by the end, which is a bit unsatisfying, but I suppose Lovecraftian horror is all about the 'unknown', so its thematically on point I guess.
Another thing worth mentioning is that for me, it wasn't scary at all. It is a horror game in terms of its story, but I didn't even feel on edge or uncomfortable at any point, I don't remember any jumpscares or reacting to them at all if there were any.
This review is supposed to be just for the base game, but I will say the DLC is great, arguably better than the base game for me. For one, it's shorter (maybe 1.5-3 hours?), which might be a downside for some, but again, for me, it again avoids overstaying its welcome. Second, the claustrophobic, isolated feeling of being at the bottom of the ocean makes for a way more scary and uncomfortable play experience. I still wasn't covering my eyes or screaming etc., but it did have me genuinely on edge and nervous at points. It felt more like a legitimate horror game.
Overall solid and definitely worth playing at some point, but don't have any illusions about it being the best game ever made or anything like that. It's a decent game though for fans of The Chinese Room's previous games or any of the Frictional games (Amnesia, Penumbra, SOMA) etc.
