The anime series jumps straight to each character's routes and their rape scenes during the 'game', with perhaps the additional H scenes from thereafter their escape from the research lab. There were not many reasons offered as to what and why these events are happening.
After finishing the VN, I find that Euphoria was deeper than it was portrayed in the series. Sure, the VN might not have a coherent plot, but it is sitll better than the anime which ignores the plot completely. Then again, I think that is the purpose of the anime series : to sell the VN.
Character and art wise I think it was done quite nicely. The voice acting was good too. Though this might be biased as I enjoyed the range of voices the VAs had to make in the VN.
I would not really recommend this if you are not into rape and rough sex with some gore and scat involved. But it did piqued my interest of the full story, but I wouldn't recommend the VN if you want a solid story, but I would recommend it for its H scenes. You could read online the spoiler-filled summary for Euphoria to get some idea what is it about, but I can assure you very few was portrayed in the anime series.
