There's an interesting take on modern economics in here. Young Lundy goes through the magic portal and arrives in the "Goblin Market" and the next decade of her life is consumed by the peculiar economic system they've got in the market.

Mild spoilers follow.

Everything one receives in the market comes at a cost. This includes finding a place to sleep for the night, having a glass of water, a bit of food, or just enjoying a warm bath. The cost is always referred to as "fair value" but that's on a sliding scale depending on how desperate you are. For the characters in the story this usually ends up being taken on as debt, and people in the Goblin Market who don't pay their debts your are magically disfigured, part by part, into a freakish bird thing. At first, our protagonist wonders how people let this disfigurement happen to them when it is so easy to just work a little bit and avoid debt-disfigurement. If only it was that easy. People living in a magical world don't want to just spend every day doing other people's dirty laundry (as the characters here do for a time) they want to go out and have adventures. There's your markets-are-terrible message.

Anyways, I do like that all of the action takes place off-page. That allows for a laser-sharp focus on the messages about work and debt and markets. It's a short novel, afterall.

Note that the book does start out a bit slow, as the author spends the first 20% of so talking in great detail about how different the protagonist is from all the other little children. That part was a bit on the nose.

This is a prequel to the other three books in the "Wayward Children" series. I guess you can read it first. Or not.