I've often puzzled over the fact that so many nineteenth century adult novels have somehow become labelled as only for children. I suspect it's tied up with this silly idea that fantasy and science fiction is only for childish adults who refuse to grow up and do properly mature things like talk about mortgages and the price of carrots. Anything to do with galloping through forests, waving swords around, and thwarting villains, whether set in the past or in magical kingdoms, is "childish." While Victorian gentlefolk, while perfectly capable of being boring and starchy and horribly grown-up, saw nothing wrong with reading tales of high adventure.