Short review: If you are into Extreme Porn, meaning Ryona/Scat/Snuff, Euphoria is a must play. If you can stomach Extreme Porn you might want to play it for the story.
The best route order if you want to experience everything is:
Makiba->Natsuki->Rinne->Nemu->Kanae
Euphoria is really 2 games. An Extreme Porn Game with excellent scenes and voice acting, and a Visual Novel with an absolutely bonkers story.
The first is great, if you are can stomach extreme content. There's a censor mode for "gory/feces CG variants", but those only hide the art, the content is still there. The Voice acting is absolutely amazing, and the scenes are quite long.
The art is good and there is great variance of scenes, almost all involving some sort of fetish.
If you are into extreme stuff, ryona, snuff, scat, the game is worth playing for this alone.
But Euphoria is also a story VN. And here the evaluations is more tricky. 3 out of 5 routes in the game lead to essentially filler endings, that end up being little more than filler to the overall story. 2 of those barely give you any info on the story itself, aside from some foreshadowing.
Almost all of the real story happens in one of the routes, and only at the very end.
The game essentially becomes an entirely different story in the last couple hours.
While the two aspects of the game, the porn game and the story VN overlap, the game is absolutely amazing. There is a lot of neat foreshaodwing going on for some of the twists in the second part.
But only for some.
Once the story leaves the porn part behind entirely, it becomes a gigantic mess of info that was not set up, a bunch of bullshit happens without reason, and is overly convoluted.
Specifically:
But that doesn't stop Euphoria from having several amazing moments in its story, and it is better than 99.9% of all Porn games.