Four-and-a-half stars, except that would be unbearably mean. The book has a serious flaw which I shall reveal in a moment.
A beautifully drawn setting, some imagined proto-China, wonderful writing. Some lovely characters, all quite distinct even within the ubiquitous formality of the cultural setting. Beautiful descriptive passages and a deeply right envoi to bring closure.
Which brings us to the plot. And that flaw. This book is too damned short. There is enough material here for something twice the length exploring more of the side-stories, which would also allow the motivation of some of the characters to be explored more fully.