Disclaimer: reviewing uncorrected digital proof via NetGalley
This story had some really interesting ideas but didn't hold my attention as well as I'd have liked. The relationship between the main character and her shadow (invisible friend?) is interesting, unique, and offers some unusual opportunities to show a story from a very interior perspective. I really liked the setup and premise. Adult readers will very quickly pick up on the fact that the shadow is a rather suspicious character, but if kids take a little longer to clue in, it still shapes up a nicely creepy, ominous and dark fantasy/horror-lite atmosphere. The setting is that vaguely Medieval Europe-ish world of stone manors/castles and rural cottages, which is a draw for some readers, but tends to be a little light on worldbuilding because it relies on familiar tropes.
The threats that launch the adventure felt unlikely; I just didn't buy into the parents' nastiness or the risk of kidnapping by enemy agents. Other child characters were handled well (kids with powers/light-magic boy & power-radar girl) but adults faded into the background. Which, to a certain degree, is fine in kidlit, because the story has to be driven by the child characters, but I felt like it stole some of the intensity, depth, and motivation from the story. As the first book in a series, it seems to be setting things up, without high enough stakes or a shocking enough reveal for my taste. However, an age-appropriate reader might not have the same reaction, and would probably experience the atmosphere and threats as more creepy.