The language in The Wee Free Men is pretty simple—it's written for an audience of wee ones, after all. And since Tiffany Aching is only nine years old and most of the story follows her journey, it makes sense that the language is simple, clear, and engaging.
Things do get a little complicated when you throw in the Nac Mac Feegles though, who have their own dialect. For example, they constantly say ken instead of know, which can get downright confusing. Once you get the hang of it though, it's smooth sailing from there… if you ken what we mean.