Out of all the anime. manga, visual novels I have read or seen, Pandora Hearts is the one that will always be engraved in my heart and the others as well.
Nothing is stereotyped about this series, there is no lovey-dovey romance for otaku basement-dwellers, instead, this manga focuses on something that has been long overlooked: friendship. It doesn't matter how old one is, its gender or anything else, friendship will always be the greatest form of love and I'm glad the authoress managed to convey this message with such a masterpiece.
Don't let the Tumblr shippers/fangirls fool you, there barely is something that can be called "romance" in it.
At first glance it may look like a comedy but it soon becomes the most complex mindrape I have ever read, yes, way ore than NGE and any other work you can consider "mindrape". If you're looking for a variety of unique characters, each with its own backstory, plenty of surprising plot twists, you just found the best manga I can recommend you.
The art is amazing since the very first chapers, and it gets way better later, I don't really have anything else to say about it, except that the art isn't really the strongest point even though it's one of the best drawn manga I have read.
As I said before, Pandora Hearts has plenty of unique characters you might want to relate with, even the "villains" have its own reasons, pasts, and regrets, as well as even mostly secondary characters being very useful to the plot and the main characters. I can't say anything about this because it would be a lot of spoiler, but I can tell you each character isn't ever being overlooked.
Once you'll reach around chapter 20, you'll enjoy it to the fullest, all your theories about what'll happen in the story will crumble, as there are many unexpected plot twists that will make you enjoy even more the manga, the authoress also loves to play with our feelings, which is another unexpected thing.
Never I had found a masterpiece as perfect as Pandora Hearts which made me laugh, cry and smile so much, all my attempts were useless, I still struggle to find a manga which could be equal to it without any success.
I am planning to re-read it soon to enjoy it all over again, as it is my #1 favorite manga I have ever read