I don't feel like going too deep into it, but this game was really great and atmospheric, and I'd say was at least a 4 star game until the ending cutscene kept playing. Like, seriously, up to and including the first half of the ending cutscene this game was great, but it kept playing and went on to ruin the entire game because due to the topic matter this game cannot stand without a well made ending, and they decided to make a nonsensical, weird in tone plot twist with forced sequel bait when the way the story had been going it should have been impossible to make a sequel. Anyway, I gave this two stars to acknowledge how good it was up to that point, but dang that ending ruined it so bad.
So I was a backer of the Kickstarter and let me just say to begin with that I do not regret funding this. I loved my time with this game, but sadly as much as I want to give it 5 stars due to my love of Cyan's works, there are a few reasons why I cannot. First, performance in both VR and flat-screen is very poor. Unlike what another reviewer said I do not believe this game has shader compilation stutter but rather I think he was noticing streaming/traversal stutter, since it happens consistently when walking through specific areas. Strangely this seemed to be worse in flat-screen mode, but that might have been due to reprojection hiding it a bit in VR. Past that I have a pretty beefy computer but in VR I could not run it above low settings, and even then it struggled due to what appears to be a CPU bottleneck. Worse is the visual anomalies in VR. As of the third patch shadows straight up don't work right on anything above low, and things like fog render differently in each eye resulting in shimmering. Flatscreen has some minor visual anomalies mostly due to their over-reliance on screenspace effects, but it's not as bad as I remember it being in Obduction. Past the performance issues, the gameplay is fun if somewhat gimmicky-feeling, and the story is captivating if spotty in parts. The worlds are a delight to wander around as in any Cyan game, and I do genuinely recommend it. It's far from their best game, and honestly I think it might, in my opinion, be their weakest, but it's still got that signature Cyan feel to it, so if you loved the Myst series and Obduction, and keep your expectations realistic, you're sure to have a good time with this one.
So, just to start I want to give a brief example of my opinion on the series up to this point: before this game SS3 was my favorite game (it has a rough start but its higher focus on story combined with the great gameplay after a few levels is really what made me a fan). TFE was fun, TSE was better because of some of the crazy parts (like the upside-down room) and more interesting settings, and SS2 is my most hated game of all time. Aside from some BS design, like the over-reliance on hit-scan enemies, I find the core Serious Sam gameplay to be one of the best twitch-shooters. Now, how is SS4? Well, I haven't quite finished it yet but it is already, by far, my favorite in the series. The gameplay is amazing: many of the hitscan enemies have been re-worked to be less annoying, as have a couple of other enemies including the Witch Brides from SS3. Yes, some of the levels, specifically early on, are somewhat sparsely populated, which is a little disappointing but completely understandable given how absolutely massive the levels are now (plus once they release mod tools I'm sure the community will go absolutely crazy with the enemy numbers). The story is easily the best in the series. Written by the same brilliant writers as The Talos Principle it of course nails the dramatic points but shows that they are also capable of writing humor. This easily has the most comedy out of the entire series and, unlike the atrocity of SS2, the majority of it is extremely funny. The only problem in regards to the story is that, first, the cutscene animations are about as jank as they were in SS3, but they manage to make it work well enough. Second, some (not all) of Sam's lines are really poorly digitized, which is a real shame because again this has some of the best one-liners in the series. Music is beyond great, too. Only real problem is the performance, but knowing Croteam it will likely be fixed eventually.
To begin with, let's start with a brief synopsis of the game itself. It can be very cool at times like you'd come to expect from Arkane at this point, but it can also be unbelievably jank like you would also come to expect from them. About 80% of the enemies are mechanically similar to the Archvile from Doom 2 with practically no way to break line of sight, all the enemies are amorphous blobs which makes basic stealth and combat a chore, the game is structured kind of like a metroidvania which really just wastes your time, and cool moments and dialogue are ruined by people constantly talking over each other and cluttered visuals. Don't get me wrong, it does some really great stuff, for instance I've never played a game before that portrays how disorienting zero-gravity would be, but the negatives make the game just overall a really hard thing to recommend. The biggest problem isn't even really the game itself, though. This game has forever buried a much better game, Prey (2006), and for that I have to remove one star. For those who don't know, this is completely unrelated to the original game. Bethesda apparently just had so little faith in the IP that they let Arkane use it for this, and that's really a travesty. The original Prey is possibly the most unique game I've ever played, and I could rant on and on about how good it is and how it constantly keeps you on your toes for what crazy thing you'll see next. The fact that this exists has sentenced the original Prey to the same fate as the original Quake, so much potential that was thrown away because they couldn't be fussed to come up with a new name. tl;dr - Don't play this, track down a copy of the original Prey instead.