Cuckoo Song by Frances Hardinge
My rating: 4 of 5 stars
The genre here is historical fantasy, or something like that. Triss, her sister and parents live shortly post-WWI, a time when there's still disruption from the veterans returning and industrialization is changing how people live. Dad is an engineer, Mom has "episodes" that require a wine tonic, and sister Pen seems to hate (really, really hate) Triss, who is one of those perpetually sick and fragile children... or is she? And is this really Triss? Pen doesn't think so.
Intermixed with the story, and the addition of the Besiders, is a semi-cautionary tale about how change isn't a positive thing for everyone. Plus, sometimes you have to let your children go and grow on their own.
ARC provided by publisher.