In The Feral Child, the fae world and the human world live perilously close to each other. One could say they overlap or overlay each other. All that would be fine and good if troublesome faes didnít all-too-frequently visit villages and steal away young children, replacing them with fae changelings.
This is what happens to young Stephen. But Maddy is not going to let that kind of fae-kidnapping stand. So, with her cousins, she dashes off into the realm of the fae.
The fae world has cosmological rules, of course. But the rules can be intuitively known, because human imagination and belief organically construe and affect them. So if a child is expecting--and sincerely believes--that a stag will appear as a guide to help her once she has crossed over into the world of the fae, then that stag will of course appear.
There are wars as well. Not the great war that the humans won, but other wars
between faes, fairies, dryads, etc. And there are rules, such as an evil White Queen. The familiarity is the fun of it. There are faerie promises and loopholes, as is to be expected from the folk of faerieland. And there are quests, battles-- mental and physical--and flights from skirmishes with evil wolves.
Stories and plots which use meta themes and parodies can work very well--or not. Often their success depends on the readerís knowledge and willingness to play along. This is a book written to be read by tweens, middle-schoolers, or read to grade-schoolers and elementary kids. There is a lot of meta-winking in the story, and those readers who are aware of Narnia will smile in recognition of certain tropes or characters. There is always a question of whether a meta-filled story is having creative fun or is using the more famous story as a template.
The Feral Child is classic with a meta vibe. There are moments when one wonders if the author relied too much on C.S. Lewis's Narnia, but if she did, she has created a good Irish version of it. Recommended.