I found this series very interesting. The only down parts, if I could say, is the pace which is so slow. But the fact that the whole series progresses realistically following the characters profile mades up with that evenly.
The part which I found interesting obviously the gender issue here. I'm just studying feminism recently. I know there's no slight relation of this series and feminism but there I also study gender stereotyping. On what was supposed for male, biologically, and what was supposes for female, biologically. The two protagonists of the series are against them, and specifically some of Nitori's inner thought are what really interests me, I also found on some Takatsuki's though. Even though their problem or thoughts were mostly personal and somewhat selfish that's the thing that made the series for me. Also you can realize it with ease that Nitori himself was criticizing the misogynist social construct. There's not much feminism but I would say this series is pretty interesting if we were to talk about gender related issue. I sure hope that the author has something in her mind when writing this series.
Also to mention the artist's art are surprisingly plain but beautiful. The simplistic story were in par with its simplistic art style. The most powerful part of the artist's I would say is the cover where she did so well with the, if I'm not mistaken, water color. I've read her other work, Aoi Hana, where she did it well too with the water color and the whole artwork of the series.
I would highly recommend this series. But I also found the issue is rather sensitive, well at least here in my place. Concerning the genre, I don't really know what makes up 'seinen' cause this series just had too much drama with it and its not the kind of drama you would normally found on 'male-oriented' works even though the crossdress might counts and the cute characters maybe. Its just simple 'mature (readers)-oriented' work for me, as the issue here should be handled unseriously but its quite serious. The gender-bender, LGBT, crossdress is not for fun but it's part of the theme brought by the story, it's the issue, the problem.
p.s. pardon me if I sound a bit arrogant or cocky or anything. I haven't read so much manga and I'm also a bit picky on choosing what manga I would read. If there's any disturbing argument with my comments, I apologize, Also pardon if there's many grammatical error, considering English is not my mother tongue and I'm not really on studying it. 😛