*Review contains spoilers*

Story 9/10
Nana is definitely unlike most shoujos out there, it has a very unique and appealing story. The story is very well executed, one event leading to another without overlapping or feeling like a device used only to create an specific situation. Transitions between arcs are very smooth and manage to keep you interested. But what I really liked the most about this manga is how realistically life events are portrayed, making characters and their emotions very believable and relatable. I was moved to tears by people's reactions to Ren's death and also very moved by the opening/closing statements in many chapters.
The are 2 things preventing me from giving a 10 to this section. The first one is that the manga was never finished, thus we don't know the real ending of the story. Some might argue that it doesn't really matter because even though the last chapter leaves things hanging, you already know what the future holds for the characters. Yet, I feel there was still more being build up to happen (such as Slutty Nana meeting with Nana Darks, Slutty Nana FINALLY making up her mind between Nobu and Takumi, among other things). The second one is that some relationships seem to just be stuck in the same loop, never moving forward or being completely finished (for ex: Nana Darks and Ren kept finding dumb reasons for quarreling and being apart rather than together, Slutty Nana seemed unable to move past Nobu but determined to remain by Takumi's side knowing she wasn't completely happy with him or happy just at moments, Nobu remained stuck on Slutty Nana, Reira remained stuck on Takumi, Shin going back and forth on his feelings for Reira...). I understand being confused, but people do need to move on. The only person I felt progressed was Yasu, letting Nana Darks go and giving himself a chance with Miu (so happy for him!!!).
I want to point out that Nana is definitely one of those literary works that you would recommend people to read the original source (manga) before seeing anything else (anime/life actions). This is not to say the anime is bad, on the contrary, it was a very faithful adaptation. However, the manga shows conversations and character's thoughts more in depth, allowing you to actually understand characters more while reading the manga than what you do while watching the anime (that happened to me with Slutty Nana, which I almost hated in the anime but came to understand and tolerate better in the manga).

Art 8/10
Art was good, not the best I have seen, but good enough. In no way do I think that art affected the manga.

Characters 10/10
I have to give this section a 10 because characters were so well developed, so many layers to their personalities were shown, that I can't bring myself to completely hate or dislike the characters I felt were the worst (*cough, cough,Takumi, cough, cough Slutty Nana*). I also must say that characters do remain true to themselves throughout the whole manga, as much as we might hate what they do or don't do.

With Takumi, there were times when I thought "maybe he is not so bad", specially because he was the only one who accepted Slutty Nana as she was and supported her (with the pregnancy) when she needed it the most. I almost settled at having a love/hate relationship with him. However, although it could be argued that at least he was sincere and straightforward and an objective person, HOW THE HELL can you tell your partner "I cheat on you but you are the one I truly love"?! what the hell?! that is not love at all!! I kept wishing he would make himself a better person, not only for Slutty Nana, but also for himself and his family (and honestly, at least he accepted that he had neglected Slutty Nana so much that he wasn't surprised she didn't want to move to London with him), but that change didn't happen. He did step up at times when he was needed, but other than that, he was very abusive and negligent towards Nana and their daughter. Slutty Nana...I must say I was able to empathise with her at times and managed to not dislike her, but I found very annoying her being so indecisive between Takumi and Nobu, and making the conscious choice of staying with a man she knew was unfaithful and didn't make her happy. I almost respected her when she considered moving out of her house with Takumi, but she endep up stalling all the time! I do think Slutty Nana represents a lot of people, or at least most people at different stages and phases in life, but I would have liked to see her actually grow up and stand up for herself, on her own, for which she had many opportunities to do.

I really felt sorry for Nana Darks, as life just kept making it difficult for her, depriving her of love and affection from those she cherished the most. She fought so hard for what she wanted, but life just kept bringing her down. I would have absolutely loved for Nana Darks to have a proper ending. Not a happy ending, because it seems the author would not allow that for Nana, but at least something going right for her! I also felt very sorry for Shin and was really glad he found a group of people that cared for him (specially Slutty Nana). Ren...obviously has issues, but I honestly felt they were not that delved into

Enjoyment 9/10
Although I enjoyed Nana pretty much I do feel disappointed that it was never finished. The last chapter leaves a cliffhanger between Nobu and Slutty Nana, even though you know that they don't end up together because in the future she is still married to Takumi. So, unless the author planned to continue the story, it makes you feel like a waste of time creating such cliffhanger if it's not going to be followed up in the future. And also...why did Nana Darks leave?? (she was doing better after a while following Ren's death) when did she go? why did people think she was dead at first? did Reira continue with PTSD? so many things left unanswered!

Overall 9/10
It's a manga worth reading, but the fact it was never concluded does rest points to the manga in general.