First off, I'd like to say that the drawing is a bit static, not always pretty, and strange compared to the typical "shoujo" manga style. As for the plot, characters, and the way it's depicted through the manga... it's all excellent.
The angst rains like mad, though, so unless you can stomach possible (?) character death, I wouldn't try it. It's one of those depressing stories where one of the main characters has a horrible disease, and while usually I can't read those kinds of stories, since they're often hideously melodramatic, I tried this one out and it wasn't like that at all (or maybe it is, and because I don't really read these kinds of melodramatic stories, I don't really know if it's that cliched). The little plot twists and the messed up relationships, and messed up characters.. this story keeps you on your toes.
What makes it more interesting is that so far it's been narrated by a guy, and though of course it sort of caters to the shoujo audience by the fact that he's so desperately in love with Mayu, it's still lends a certain intensity/change of perspective to the manga that you normally don't notice, what with the perspective mostly being biased towards girls (though a notable exception I think is Stroke Material xD😉.
So, if you don't like tragedy-type romance, it might not appeal to you, but the romance/relationships are interesting, and the plot is very intense, and the perspective is different but it works in this type of story, though it does some brief interludes with Mayu narrating. The drawing is .. a bit bleh, but there are some nice parts, and it conveys the story rather nicely, though the way she draws eyes bugs me a bit. Still, it's worth it to read it. It's one of those stories that I wouldn't miss. ^^