One could criticise fantasy by saying how unreal it is… In other words: Magic wands don’t actually work, so why read about them? Well, to answer that question, we must first ask ourselves how we should think about reality, before we try to think about unreality.
There’s this thing called induction: One sees one specific thing happen happen every time another similarly specific thing happens. The more we see this relationship occur, the more we realise that there is a pattern, and that pattern implies a rule.
We can’t see these rules directly, but we can see them indirectly. Our ideas are a model of the world based on the way we see it function. If you really think about it, we are only as certain as reality as we would be about the inner functions of a computer game (don’t let this fact destabilise the rest of philosophy, knowing it eventually sinks in and life becomes normal again ;).
The thing about reality is that it is, essentially, coherent and consistent… and so long as a fantasy novel shares that property, it is somewhat as real as reality. It’s a experimental microcosm that is brilliant because it doesn’t need to abide by all the rules.
I see fantasy and fiction as a detailed tinted mirror, that reflects reality in a way we haven’t seen before, meaning that when we turn away from the mirror (which I would recommend, escapism kind of misses the point), we find reality fuller and more interesting than we otherwise would have.