"Elfen Lied" is an INTENSE psychological anime, especially when the viewers pieced together information from the first few episodes and have already figured out what Lucy did to Kohta's family. But Kohta and the others are, of course, clueless; leaving the viewers scared about whether or not Kohta and the others are in dangered and whether or not Lucy would survive.
"Elfen Lied" has insanely good animation for an anime that was produced in 2004, but I'm not too sure about how good the story is, actually.
The concept of research facilities experimenting on humans who were born differently than others might not be all that unique. I mean, that kind of happened in real life during the Holocaust. But the execution of the concept is pretty nice, allowing the viewers to see the humane sides of characters who were deemed to be evil from the very beginning.
I also liked the use of flashbacks, adding onto the suspense I felt and messing with my head a little bit.
What I did not like, however, was how fucked up the relationships were. We know from the beginning that Yuka likes her cousin Kohta. WHY? There were some other things that would be spoilers, but most likely, the author just wanted to have these fucked up details because "Elfen Lied" is a pretty fucked up anime. Anyone can tell how fucked up it is going to be from the opening/first episode. Like, since when was there nudity in the earlier anime series?
Anyway, I liked the symbolism in the last episode, even though it did not give me a good sense of closure.
I would recommend "Elfen Lied" to anyone who is looking for an intense, fucked up ride, but it's not really a masterpiece, no.