"I sometimes wish that I could control the weather. But this might be uncomfortable for other people."
Urban fantasy, in this case, I'm describing as when creatures from other realms or from the past or mythology come into modern Earth. This can be done really well, as witness most of Charles de Lint's books. (Not Spiritwalk, though).
And, on the other hand, it can suck like hell.
1) Too often, the non-humans are prettified. This happens most often to elves, especially the elves from Mercedes Lackey's SERRAted Edge books, but almost any urban fantasy story with vampires does the same thing. Any nasty aspects that might emerge from the original mythology- which is worth paying attention to if these creatures are supposed to be the same ones the legends were spun about- are wiped away. The elves don't steal children and leave changelings in their place, or make someone dance until she dies, and they aren't fey and fickle and cruel. They steal children who are abused, since they are, of course, Good. And it's those nasty Unseelie who were responsible for all the other bad legends, of course! (And the Unseelie are as flat as the usual fantasy cartoon villains. See Point 3). The vampires don't suck blood and rejoice in it, or even just act as casual predators. They are Tormented. They are Angsty.
You'd think that, if these creatures from mythology really are like this, there would exist more legends of weepy vampires who only want to help the living out.
If the creatures come from another world with its own legends, then this objection falls away- but, too often, those legends are supposed to be the exact same ones that spawned on Earth, so that elves from Fairyland really are the ones that gave birth to the legends of the sidhe. They just happen not to live on Earth. And, you guessed it, they are shiny and Good.
Why choose prettified versions of non-humans? Why base all the elves on Tolkien's? He took them through a complete transformation from the original legends, partly by writing a lot of history from their side. If urban fantasy is about humans engaging with deities and the fey and unicorns, as it usually is, then we as readers are seeing these creatures through human eyes. The legends should come into play. And not only the pretty ones or the versions popular in the modern fantasy genre, either.
2) The human heroes of urban fantasy are almost never ordinary people. Weirdly enough for a genre set in modern Earth and involving the interaction of "fantasy" creatures with the usual Joe on the street, there are almost no Joes on the street. Everyone that can actually see the elves or interact with them is cut off from the mainstream in some way. They're Wiccan, or they have magic, or they're reincarnations of fairy princesses, or they have elven blood, or blah blah blah and so on with other things that move the genre away from the "urban" part of its name.
I would like to see urban fantasy that deals more with what we think of as the mainstream- people who have never believed themselves to be psychics or mages, gas-station workers, Christians, housewives. I think the confrontation would be deeper and richer with people who aren't already predisposed to decide that elves exist. And lifting a focus off religion, non-human blood, or magical powers gives the authors free rein to make the characters special in another way: making them extraordinarily intelligent, or witty, or courageous, or practical.
Part of it's personal bias, but I adore fantasies where the author makes heroes by creating people with magnifications of ordinary qualities that anyone could have. It makes reader identification easier, for one thing. I don't believe for one moment that I'm descended from fairies, but I could, I hope, see myself as being courageous enough to enter a burning building to save someone I loved even knowing a fire demon was there.
3) The moral complexities of the modern world get ignored. Another case of shoving aside the "urban" part for the "fantasy" part. I would assume that part of the reason authors want to write urban fantasy is for the sake of dealing with Earth's historical events, social trends, and people. However, that rarely happens. Instead, they create a self-contained world of elves, unicorns, giants, and other beasts with supposedly flimsy shields (see point 4) separating it from the cities. Those shields are thick enough to keep all ambiguity of motive out, though. Instead, within this little area, a typical fantasy goes through the motions. The villains, human, Unseelie, or other, are unrelievedly dark. The heroes are unbearably good. The "ordinary" humans (see Point 2) drawn into this world are likewise unbearably good or unrelievedly dark. It's as if the tangled, complex, mutable world they lived in before the mythological creatures showed up just vanishes. They never doubt that what they are doing is right, or that what their opposite number is doing is wrong.
It's so very strange.
Barely, just barely, I think authors can get away with that in another realm, since that world's social events are different, and the universe itself may be moral at the author's whim, while we don't know if this one is or not. When it happens in urban fantasy, it completely shatters my suspension of disbelief. I might be able to accept that elves are completely Good and Unseelie are completely Evil; I cannot accept it about modern Earth humans.
4) Secrecy is simultaneously an important concern and half-assed. Sometimes it seems as if the self-contained little fantasy world skims along an inch away from discovery. The elves disguise themselves as humans and hold human jobs, but have different needs and physiology that could give them away. "Ordinary" people are always stumbling in. Magical battles run the risk of being seen by outsiders.
Does anyone do anything about this? Not most of the time. The authors resort to implausible coincidence instead, such as having every human who stumbles into the magical world have some reason to be there (see Point 2). They can't have their elves set nasty traps to destroy intruders, since of course that would shatter the idea of elves being completely Good. And god forbid they have them engage with the ordinary material of life such as motion sensors, electronic tracking of identity, or registering to vote or drive a car. It somehow all magically happens, even when magic is supposed to be hard and dangerous to use.
This is one thing that deeply impresses me about Rowling's Harry Potter series, simple as most of it is: She at least takes the time to note that there are precautions to keep Muggles from stumbling into Hogwarts or any other part of the magical world. When something magical does happen inside Muggle eyeshot, then there are Oblivate spells cast to take away the inconvenient memories. At least there's no forgetting about it or mention of it "being taken care of" without specifying how that happens.
5) Here we go with the "magic is fading for no apparent reason" thing again. This is where it's a good idea to choose your urban fantasy creatures carefully. Dryads would have a good reason to die off in the modern world, since they traditionally depended on their trees for life, and a logged tree means a dead dryad. You could make a similar case for sea creatures like mermaids, who probably wouldn't be able to flee water pollution forever. But what about creatures from other realms altogether, like sidhe in their hollow hills? What about the creatures said to dwell in common with humans, like trolls and brownies? What about those able to turn themselves invisible, shrink themselves, or adjust their physical proportions to changing circumstances?
Why are they always dying off? If they're intelligent, it doesn't seem out of the question that they would be able to adapt as humans have to natural disasters, and even use their magic to conquer nature. Instead, they seem bound to it and fading helplessly. Sometimes this has a good base; one of the few things I liked about Mercedes Lackey's books was that she had elves be afraid of iron, so their magic faded around it. (That begs the question of how the elves could walk cities like New York at all, but at least she made some attempt to address it). Other times, it doesn't, and it's just the "Let's make these elves the last of their race because it will be dramatic" kind of thing.
Try to have a good reason for the fading of the magic or the deaths of the magical races in your urban fantasy. Perhaps they humans have become boring to them, and they have withdrawn to their homes. Perhaps they have become something we no longer recognize, and which are too new to have legends about. (What about supposed gray-skinned aliens as another form of trolls?) Or perhaps they aren't fading at all, and are happily splashing around in our lives still.
6) This subgenre is probably the one in which the "magic= good/technology= bad" divide is the most severe. Humans and their damn technology, runs the undercurrent of a lot of urban fantasy. Magic was better. The days when humans lived in caves and hunted with spears were much better, compared to this. Elves, old gods, vampires, and what have you are the true lords of the earth (never mind all that inconvenient messy mythology which, taken as truth, would say some pretty unpleasant things about those lords).
This doesn't make any more sense to me than the desire to create a little self-contained fantasy world does. Isn't part of the drive of moving into twentieth-century (or twenty-first century) Earth the desire to engage with technology, to see what happens when an elf tries to drive a car, or what a vampire makes of the Internet?
Apparently not. Whether it's the Luddite strain a lot of fantasy writers have inherited from Tolkien, or a blinkered drive to always regard technology as the problem instead of the creation of humanity, most urban fantasies take the opportunity to savage cars and computers and all the rest. See all the other points.
Urban fantasy is another genre that's often simplistic and shallow, and it doesn't have to be.