It's... very moralistic. In a 19th-century, Christian fashion. HOWEVER, I still love it. It's such a ridiculous story and the bit about the School of Pain made me want to vomit (in fact, it reminded me of a stupendous article that appeared in Lupus UK about how chronic illness is really a "beautiful beast within" which is actually the most offensively stupid thing I have ever had the misfortune to see in my entire life, including that film where Jack Black is a luchador) but otherwise there is something so wonderfully compelling in the Katy character that will never make me able to hate this book despite me disagreeing with this whole moral construct. I don't actually think Katy is a less interesting character after she "grows up". There's nothing wrong with learning to be patient with others and to love your neighbour and try to see the best even in the worst situations. It just shouldn't be presented as a requirement of personhood. Anyway, compared to all the other turn-of-the-century sentimental crap that came out of American children's literature (Little Women, Anne of Green Gables, Pollyanna... VOMIT) this is a lot better, and I remember enjoying the sequels too! Good to read on a tiring journey.
