Major spoilers for Elfen Lied (Read this review after completing the manga)
After completing the Elfen Lied anime, I decided to read the manga since it has a fully completed story. And it was definitely the right choice.
Story-The story in the beginning felt kind of bland and fillerish to me but maybe that's because the anime already covered the beginning volumes of the manga. Around halfway through the manga things start to really pick up and shift into high gear, having lots of twists and turns that make my heart ache. There are many unnecessary fanservice scenes and a god awful romantic subplot, but luckily the romance subplot ends midway so overall I'd say the story is pretty good. 8/10
Art-This ones definitely more subjective but I do like the mangaka's artstyle for Elfen Lied. It feels a bit cartoony and cutesy but it doesn't worsen any graphic and shocking scenes, in fact it may make them feel more shocking. The art does indeed improve over time so I won't say the art makes the manga terrible, but the art isn't anything phenomenal either. 7/10
Characters-The mangaka does a great job at changing perspectives on a specific character and such. Like for example, Bandou is at first an asshole and a "villain," but there'll be times when you root for him and hate him again right after because of his actions. Same thing goes for Lucy, you sympathise with her past and it makes her actions somewhat understandable but there are times where you will hate her for what she's done, she even feels like the villain at times. This is very nicely done so where there is no black and white characters, Lucy can be seen as the villain for killing many innocent people but the Military can be seen as the villain for experimenting on Diclonius and experimenting on them However Kohta and Yuka are a different story. Kohta is really bland and your average "self-insert" protagonist and the only time he's showed pretty much any emotion was when he found out Lucy killed his sister/father, Yuka is the most hatable character in the series, she never shows a good side or acts nice, she always whines about Kohta loving Nyu and always abuses Kohta too. Overall, the characters are very well-written as you can shift your thoughts on them very easily without their personalities being changed dramatically and both opposing sides of the story have understandable reasons and no side is truly right, though there are a few bad apples. 8/10
Enjoyment-This one is of course the most subjective one, but I thoroughly enjoyed this manga, especially after the 1st half. Tensions rose high and many plot twists arose. The brutal tendency of the manga also made me immersed in it more since the mangaka wasn't afraid to touch upon these uncomfortable subjects, it really made me wonder who the real monsters were. I do wish that the "Nature vs Nurture" theme was more touched upon in the manga than in the anime, but it didn't bother me too much. 9/10
TL;DR-Elfen Lied is an amazing manga with great characters and a great story. There is no truly good or bad side since both sides have done bad things which I love. The characters can go from likeable to hatable within a span of one chapter while fitting into their personalities and motives. Kohta and Yuka are not very well written though, and the art is decent. The beginning of the story is also pretty slow and pace and relies on plot convenience at times, but that can be ignored after the 1st half of the story. 9/10
Side Notes: Favorite character was probably Kurama, since he felt like the hero most of the time in both the anime and manga. And also with all the bloodshed and nudity in this manga, i felt a certain peace to it and I can't explain it. It gets amplified much more with Lilium