The writing is atmospheric enough to sustain interest through the patiently paced journey; even when the situation the characters are in is sort of abstract, the details and the descriptions keep it grounded. I do wish the game went a little further with its imagery, though, even if I get that it's not the point – while the overall mystery of what's happening here needs no further answers than the ones already implied, I think it could have felt more distinct and interesting. The prose finds monotony and solitude in the emptiness, but doesn't quite reach the kind of haunting beauty that would elevate it further.
Along similar lines, I think the connection between the two characters remains more unspecified and hollow than it could have been even in the thematic confines of what the game is trying to say. Compare and contrast with something the game really succeeds at: the nonlinear plot. The repetitive structure of the reader playing through multiple times to get all the endings allows it to have its cake and eat it, too, with the initial run creating a baseline of expectations and the final one pulling off some dazzling twists that recontextualize everything that came before.
I wish the relationship between our characters would have been reframed or elaborated upon in a similar manner. You could introduce them as strangers meeting in this world by chance at first, doing basically what the game is doing now, and then dig deeper in subsequent endings. Unfortunately, in what feels like a major missed opportunity, there is not that much more to it all; I think the flashbacks we get aren't enough to truly explain and characterize what these two mean for each other. It does feel like kind of a bummer when it's what the emotional stakes are really resting on.
Still, the VN is a pretty good read on the whole. Ian's design is quite pleasant to look at, and the expressions do a lot to suggest character, which is very lucky when the visuals are so sparse otherwise. Plus, no spoilers, but the formal trickery in the last ending is just so fun. The stock backgrounds do maybe feel a bit generic in a way that underlines the vagueness of the setting, but it's all professionally put together – the only thing that feels underpolished is NVL mode not being styled like the custom UI component (the font isn't even the same).