To put it shortly, I'm big on MR BIG. For a jam VN, it's quite... big at 30k words, but not a single scene feels out of place or too slow for its own good; in fact, if there's a complaint about pacing to be made, the finale is maybe a bit abrupt in contrast to the story's otherwise patient escalations. When the mystery started to unravel, I was ready for it to be an "end of act 2" kind of thing, but then we just went immediately to the ending. Let this, though, read less as a criticism and more of me just saying it was so good I wouldn't have minded getting more.
The game is excellent holistically, I think. The prose and the dialogue are confident, the freaky art direction sets the stage perfectly for a game featuring a lot of sex that takes a turn for the grotesque or the awkward, and the plot is brimming with smart payoffs. A subtler thing that stands out for me is the incredibly precise control of tone & genre; when you really strip it down to the basics, the premise is incredibly schlocky in all the right ways, but it doesn't feel like that when you're reading. The character drama is so well-written that you're just invested in the protagonists and inclined to take the increasingly surreal and concerning incidents at face value.
Starting with the characters and earning the reader's interest with them instead of teasing the horror elements is really why it all works, I think. The structure is unusual for something that's unambiguously a horror story or at least transitions into one by the end, and it's good that way. (I just made myself a little angry by imagining a Hollywood adaptation of MR BIG that opens with, like, a prologue explaining what the hypnosis tape is... sorry but test audiences weren't hooked immediately!)
This is one of the entries I only got around to checking out much later than everyone else, so I don't have a lot to add to all the conversation that has already happened. It's just good, very good. One last small nitpick, though: the use of italics and bold can get jarring when the writing is usually strong enough to not need that extra bit of emphasis.