First, I should probably address those who questioned why I never played this VN before... the answer is that I did try this VN 'way back when' and couldn't get past the prologue. To be frank, the prologue of this VN is pretty... unimpressive. However, once you get past that prologue, you are put into what probably amounts to the best nakige I've ever played.
This VN is a kinetic novel, with only a single ending. It combines elements of mythology, mystery, fantasy, and psychological horror (relatively mild) into a single whole that is greater than the sum of its parts. For those who love Araragi (to be honest, I think all of those who read this VN love Araragi) more than Hiyo... my condolences. There is only one path and it is Hiyo's.
The child-version of Hiyo in the pic above is part of one of my favorite early scenes in the VN and the scene that pretty much locked in my love of the characters as a whole. I'm a sucker for appeals to emotions like the ones in this VN, and there is very little in this VN that doesn't appeal to your emotions on some level. The warmth and kindness of the three girls closest to the protagonist and the dynamic between the four of them is central to most of the story. While Hiyo-love indeed has a big impact on the story, romance in this VN is ultimately merely one of many themes, ranging from the obvious 'love of art' and 'autumn', to 'the nature of kindness'.
For those who have seen the opening song on youtube... you should probably be aware that the entire OST for this VN is on that level or better. Like many of the best VNs out there, the musical direction and the choice of music in general is superb... a work of art. There are many Chinese-classical and hybrid Japanese-classical themes mixed in with various other types, and this adds to the atmosphere created by the 'old Japan' design of the school and dorms where all the events of the story take place. These aspects, combined with the plentiful expressions and poses given to the characters' tachie, are used effectively to create the 'personality' of the VN as a whole.
The most important way to evaluate VNs that fall into the 'nakige' category is how much they made you love the characters, thus giving you a reason to cry for them. In that sense, I can honestly say that it leaves almost every nakige I've played in the dust (including all of Key's). The lack of massive casts of heroines and multiple paths serves to make every occurrence in this VN feel 'real', adding more impact to the sorrow, joy, hope, and pride that continually break your heart. I can honestly say that I feel Propeller used the 'kinetic novel' format to its fullest, succeeding in creating a story with an impact far in excess of what it would have possessed if it had been a multi-path story.
Now... I feel it is about time I stopped praising this VN and spoke about the one issue that bothered me, even after I finished it...
... it truly amazed me how bad the VN is during the initial stages. It feels awkward and forced, and that sense of 'eh, what were they trying to do here?!' is so strong at first that it was enough to make me drop this five years ago without a second thought. Of course, back then I hadn't been as thoroughly 'trained' by years of playing moege that are far worse than this... but it is still a flaw in an otherwise awesome VN. That said, once it gets started, this VN is really, really hard to put down.
Overall, the only people I can't recommend this to are the extreme moe and dark fantasy fans. For all that the designs are most definitely moe, the degree to which the characters suffer in this VN will be a bit much for the soft-moe addicts. For the dark fantasy fans... you'll probably be a bit put off by a lack of action and murder. This VN has precisely one action scene that would interest that type... and it isn't that long (though it is important to the story in general). Everyone else? If you can make it past the prologue, I can guarantee you'll fall in love with the characters, even if other aspects bother you.