This book is an interesting look at gender and gender roles in the Heian court.
The translation is serviceable, but the writing felt a bit lackluster - though I did wonder a few times how much that was the translator and how much that was the original. There were a couple of scenes where characters or events seemed to appear from nowhere, which was confusing, and there's a lot of places where the characters just tell you their emotions in very plain terms for a paragraph. And the constant descriptions of how beautiful everyone is are often vague and even more over-the-top than they are in Genji.
However, for the two siblings at the heart of the tale, who spend much of the story acting in roles contrary to their birth sexes, Willig did make the excellent decision to use pronouns that refer to their social personas. So the AMAB sibling, who is shy and goes to court as a woman, is referred to as 'she' while officially in that role. The AFAB sibling is still referred to as 'he' even after giving birth to a child but before officially swapping social roles with the other sibling.
For a modern reader, this does make it even easier to read the story as a tale of two transgender siblings who try and ultimately fail to live as their true selves, and from that perspective, it's a painful but interesting read. The two of them manage well for a while, but not without some difficulties due to their birth sexes (for instance, the AFAB sibling has marital difficulties due to being unable to sleep with the bride that are the root of a lot of the romantic drama of the book).
While their situation is certainly looked upon as an unfortunate fact - their father repeatedly worries and rues that they are like this - at the same time, they encounter sympathy. Their father allows them to have the coming-of-age ceremonies correct for the social roles they have taken on, their mothers seem supportive of both their original interests and their role swap, and a prince-turned-monk who finds out is quietly understanding. Both siblings also experience difficulties in returning to the roles of their birth sexes. Although I think the ending was supposed to feel happy and like it was a good thing the siblings returned to their 'natural' roles due to the influence of Buddhism - the AMAB sibling attains extremely high rank, and both of them have lots of children - to me, it felt like the AFAB sibling, in particular, was never happy in the cloistered female role demanded at the time.
There's also a lot of love drama, including a love triangle that spans most of the book. While it was tedious at times, I did like that the instigator, who sleeps with/rapes the AFAB sibling while in the male role, never find out what happened after the siblings switch roles again. He was a jerk, and it was satisfying that he was left in the dark, while their child together does discover the truth. The cast list was also constrained enough that I was able to keep everyone and their dramatic relations straight without too much trouble, unlike with Genji!
The book was overall clunky and a bit dry, but worth finding and reading as someone interested in these themes and time period.