This game feels like the culmination of the genre of twines that started with howling dogs. It might be overstating to call it the apex of twine, but that's how I personally feel.
SPY INTRIGUE is a story with many layers to it, and somehow it works on each of these layers as well as all together. At the beginning it seems to be a wacky, vaguely sexually charged spy adventure. Then you die and see a story about mental illness, gender, relationships, living in A Society, and all that, all excellently written. But deeper into the spy missions, the themes wrap back around into full earnestness in a way that's difficult for me to describe. I usually bounce off video game comedy, but the humor in this game is genuinely funny. (Spoiler - click to show)For example, the best updog joke in video games. Hearing the word "mumps" still makes me want to laugh in a socially inappropriate manner; I wish I could talk about "SPY MUMPS" irl without being ostracized.
I love the interface too, especially the story map, which shows the current node and all the nodes leading out of the current node, annotated with colors for whether they lead to death, an aside, or story progress.
(Spoiler - click to show)One of the segments, the death scene where the protagonist tries on their parent's clothing, really got to me in a deeply personal way; I still go back just to read this one passage.