This picked up on a couple of genres that have been fairly well-trod, but was so well written they seemed fresh and propulsive. Helen and Edith were likeable and relatable, and the prose was direct but enjoyable and descriptive. The use of magic was well thought out. I thought the short length benefited the book, it made its points and got in and out.
One nitpick is that a lot of the characters' ages seemed off. Chronologically they were mid-20s, but it feels like Helen was written as older.
The thing that stands out most to be is that it's written so well it leaves you wanting more, but also explains to you why the story's a closed loop, and shouldn't continue beyond what was written.
Even though Helen knew the end, it's not going to stop me from speculating that their story after the book plays out differently. Hey, …