Around nine or ten, a lot of readers still want a castle, and they also want a plot that lasts longer than a picture book. These novels start from a fairy tale and then argue with it. The girl who has to obey, the dragon who would rather have a librarian, the village that trains princesses.
Ella Enchanted and The Frog Princess are the easiest doors in. Dealing with Dragons is funnier and a little stranger. Princess Academy is the one to hand over when they are ready to stay with one place for a whole book. Fairest is better after Ella, because it lives in the same world and expects a more confident reader.
The curses in these books are the story, not a jump scare. Even so, read the first chapter nearby. You will hear whether the sentences are too dense.
If they finish one, the next book is the point. A fairy-tale novel usually belongs to a series or a shelf of cousins.
Leave the finished book on the desk. A reader who can see the next spine will usually open it without a speech from you.