A fictional world is defined by the people in it, and the things they hold in common. Things like fairy tales.
These stories introduce a world other than the one I live in. It shows what the people of this world value. Self-reliance, courage, cleverness, charity, and of course, justice. Where one can be cunning without being deceptive.
This world is different enough to be novel, without being so alien I can't understand it.
Plus, they are also good stories.
If I were to review this book with a single sentence, it would be thus: Thank goodness for intelligent characters.
I've seen many a story where someone seems to have told the author "Don't have them go straight into being a loving couple, it'll be boring."
And so, for reasons that stretch both credibility and characterization the couple squabble and fight until eventually realizing that they really love one another and forming a relationship. Something that the audience never had any doubt of.
Not so here. Intelligent characters coming from different places have genuine problems working out their relationship issues. And they're honest relationship issues rather than simply being inserted by authorial fiat and having no explanation save stupidity or irrationality on the part of the characters.
Now, the world is well constructed carefully and consistently with excellent attention to detail, and I appreciate that a lot too.
But quality characterization like this is rarer than quality world building. Rarer still to find both together.