Some of these panels must have taken them days each, and while the story hints at a wider universe filled with interesting things we just don't see any of it. It's light on explanation, heavy on imagery, and while it is a beautiful read there's not much story here.
The length is really the killer here. The characters, the plotlines, the backstory, the ideas, the themes, everything just doesn't get explored because it's a single volume wiht only 5 chapters in it, one of which is background and another is more beautiful artwork. It's the sort of thing you could see being a collectors item for people who loved the OVA, but as someone who hasn't yet seen it I can't say if it really works as that.
Definitely a beuatiful thing to have for the artwork though, but sadly not much else.