Leo Elijah Cristea weighs in:
Fantasy, of the epic and high variety, doesn’t much lend itself to mythology. Writers can craft beautiful, engaging mythologies for their made up worlds—I’m looking at you, Grandpa Tolkien, and you too, Mr Rothfuss—but there’s a distinct lack of familiarity that is lost. It just becomes part of the story. It’s not really mythology. To the characters, yes, but not to the ever hungry reader.
That’s where urban fantasy becomes a beautiful, magical thing, offering something that other subgenres of fantasy couldn’t possibly hold a candle to. Instead of reading about Tehlu and his angels, and the way the world was craft by this god or that god, we get to read about trolls under bridges, the fae courts, fallen angels, werewolves, vampires, Norse gods, the Almighty—the list goes on.
We get to read about magic we know, understand and believe. On some deep level inside most readers, you never stop believing. It doesn’t matter what in, but when you’re alone in the dark and there’s a tree groaning under the weight of its branches, or a chill across the back of your neck, if you have imagination to spare, you believe in monsters. You believe in Things. That’s why urban fantasy is so inherently good when done well, and when it draws on a veritable landfill of material.