Elfen Lied is a very dramatic anime that really makes you think and wonder about yourself.
The story is that Kohta and Yuki are walking on the beach together when they find a beautiful naked girl lying on the beach. Since she has no home and cannot speak, they decide to take her in and name her Nyu. However, Kohta is having haunting memories of watching his younger sister and father brutally murdered by someone. Yuki assumes that Kohta has feelings for this girl and starts to get jealous. Later on, more girls join up with the family, including Nana, a Dycoloius like Nyu, and Nana is really sweet and kind, and Myua an her dog, who ran away from her rapist step-father. But soon Nyu starts to show a dark side to her....
What I liked about the anime is that it has a dark portrayal of the human race, like making you pity certain characters based on their appreance, even though inside you know they're terrible people. The main good characters were really well-done in their personalties, making them really easy to relate to. I also loved the theme song, Lillium.
Things I didn't like about the anime is mostly that I think it needs to be a bit longer so they can explain the ending better. I also hated the gore in the anime, I felt like it was too over-extterated. I HIGHLY doubt if your head gets cut off that blood will spurt everywhere all over the room like an erupting gyser. Some people have also complained that the main villians in the anime were too one-dimisional, so I'll note that as well.
All in all, this is a really wonderfully well-done anime. The gore might put some people off and that's fine, but at least give it a try at first. It's an adult anime that isn't filled with erotic anal rape scenes, and while an adult anime like that is rare, this anime has the physocological factor down perfectly. It's worth giving it a watch.