Nana is the best shojou I have ever seen.
Despite the art being not being the greatest I've seen the writer of Nana makes up for this by creating a stunning and mature story. There is a formula that most animes/manga follow when it comes to romance, but this one breaks the mold. The chracters are amazing and realistic. You will love some, you will hate some, and you will feel so many emotions as you cheer for Nana and Hachi to find happiness. These characters are very flawed and very human which makes them easy to identify with. I would suggest that every girl watch Nana at least once.