(WARNING: RANT MODE HAS BEEN ACTIVATED. Extreme snarkiness, rudeness, and foul language beyond this point. All those overly-sensitive, proceed at your own risk.)
Nothing ruins a fantasy story for me faster than a terrible romance. Or bad characterization. Or shitty worldbuilding. Or a cliche, overdone plotline. Or a Mary Sue.
But a close second would have to be witnessing the element of magic being ripped to shreds by an author who doesn't know how to fucking write magical things so as to not ruin them.
Now, I'll be the first to admit that I'm no expert on the subject; Hell, I'm just an amateur fantasy writer myself still in the midst of building my own magic system for my fantasy world. And of course, what with it being magic and all, you really can't--and shouldn't--bind it by any hard and fast rules. Magic takes all kinds of fantastical forms and means something different to each fantasy writer. That being said, it's totally possible for an author to suck all the magic out of magic if they suck at writing it.
"But Leanne," you might ask, "How can someone be bad a writing magic if there's no wrong way to write magic? Isn't everyone entitled to do whatever they want with their own fantasy world?" Well, yes and no. This is where you'd be wrong, dearies; it is in fact possible for authors do wrong by magic in their writing. How? By trying to explain or justify every little fucking thing and not have a clue what they're talking about.
Once upon a time, humans lived in a world in which everything which could not be explained by reason was attributed to the supernatural. Magic, miracles, etc., it all boils down to the same thing. Of course, it's in our nature to seek answers. Humans love to be able to explain everything; we're curious bunch with an unfortunately high population of know-it-alls. So now that modern science has reached such an advanced stage, of course people with no understanding of a scientific subject are going to latch onto science leech from it half-baked explanations for everything they can think of. And yes, this includes magic.
I know a lot of you are probably seething at me right now. Of course explaining your world's magic is a good thing! How could it not be? Well, it is if you over-explain. Or do a half-assed job of it. Yes, it IS often a good idea (and often expected of you, depending on the role of magic in your story) to have rules and limits, though this depends on the nature of the magic itself. And yes, sometimes having too many rules and limits on magic can be stifling. But that's not the point I'm trying to make, this isn't a post about the limits of what magic can do. It's about how bogging down a fantasy with too much pseudo-scientific crap can take all the magic right out of it.
Because we as humans love explanations are are constantly demanding a better understanding of the world around us, a lot of writers make the mistake of thinking that not having a watertight explanation for everything will break the readers' willing suspension of disbelief. Ok, yeah sure, buddy. Uh-huh. Suspension of disbelief doesn't work like that, and that's not why people read fantasy. We read fantasy to escape the real world, to experience something fantastical that couldn't normally be explained in real life. Ok yeah, so there are plenty of times when outrageous, poorly written, and just plan silly things happen in books and movies marketed as fantasy that make me raise an eyebrow, like a deus ex machina, or a good ol' fashioned overpowered bad guy, or all the wire-fu used in the Twilight movies. But you're just as likely to lose an audience when you overindulge in explanations and technobabble that you yourself don't quite have a complete grasp of.
Speaking of Twilight, there's a reason why I mentioned sparkly vampires in the title; Stephenie Meyer is numero uno on my list of violators of this unwritten rule of magicbuilding. And before any Twihards start complaining (Do they still exists? Is being a Twilight fan still a thing?), yes, I am counting this as an example of magic. I don't care how you spin it, vampires and were-creatures are supernatural, and for the sake of argument supernatural=magic. "Paranormal Romance" my ass, this crap still counts as fantasy, and a piss-poor excuse for it at that.
Let's start with the obvious: I don't care that her vampires sparkle. There, I said it. I still think it's a stupid plot devise, but the mere fact that they sparkle doesn't offend me. No, it's the how and why of the sparkling that makes me cringe. Someone else has already done a beautiful job explaining this here, but I'll do my best to disassemble my reasoning for being so pissed off.
See, if Meyer really wanted her vampires to sparkle, it wasn't really all that necessary for her to jump through all kinds of hoops to try and justify it. Sure, I still would've rolled my eyes at it, but I would've accepted it just fine if she'd said that as predators, vampires use their sparkliness as a way to distract or mesmerize their prey long enough to go in for the kill. Sounds reasonable enough to me, and in fact this seemed like what she was going for. But, considering the fact that Meyerpires are nigh-invulnerable, practically move a light speed, and no human or animal could possibly out run them, it renders the whole point of them sparkling as a predatory technique moot. And of course the "how" of them sparkling is equally stupid; basically it boils down to vampire skin turning to stone with crystalline properties. WTF? Let me just clarify, there is nothing wrong with having moving statues or sentient rock-like creatures in a fantasy; after all, magic tends to possess that MAGICAL ability to make the impossible possible. But that's the catch: Meyer digs herself into a hole by trying to scientifically explain how it's possible... and in doing so makes herself look like an idiot who doesn't understand basic biology (for more information, follow the link above for a sporking of the Twilight Illustrated Guide). And really, what purpose does making vampires into stone serve? Wouldn't it really just make more sense and save a lot of trouble to say that they have really tough skin which also happens to be a bit shimmery due to magic radiation/glittery vampire sweat/OR perhaps even better, an illusion created by the vampire himself? Vampires in fiction are traditionally know for being masters of illusion and manipulation, after all...
This is just one of the many examples of jarring idiocy present in the characteristics of Meyerpires. Let's take a look at their fangs, shall we? Oh wait, they don't have any, just normal-looking razor-sharp teeth! Sounds great, but there is a reason why most traditional vampires have fangs, it's because it's an efficient design that doesn't make a bloody mess everywhere. But wait, if they don't have hollow fangs (like a snake), or even fangs at all, how does this "venom" come into play? Great question, because even though Meyer goes to great pains to explain how venom is in saliva and apparently somehow replaces all a vampires bodily fluids, no of it makes any goddamn sense. And if vampire teeth are razor-sharp and constantly coated with venom, then how doesn't simply making out with Edward turn Bella into a vampire? See how quickly this all falls apart?
Some of you may think I'm being too nitpicky. But am I? I know I'm not the only one out there who is bothered by all this pseudo-scientific bullcrap. And the real point I'm trying to make is that once you start over-explaining, it's hard not to fall into the trap of overthinking EVERYTHING, while at the same time leaving gaps in the explanations that stick out and make you look stupid because you tried to explain everything else. It's not all or nothing when it comes to mixing magic with science, but there is a threshold, one which Stephenie Meyer definitely crossed. If you're going to give us a bullshit reason for why vampires have venom in their eyes but not tears, then you should be able to explain why vampire eyes are red, and why they turn gold from drinking animal blood. Normally a simple "because magic" explanation would work just fine--you don't need science to explain eyes with magical properties in all the thousands of places they show up in media--but in this case it just seems like bullshit piled on top of more bullshit.
Of course, there are other know-nothing know-it-all writers who suffer from a less severe case of Explanitis than Stephenie Meyer. Sometimes over-explaining/inconsistent explaining isn't the problem, but there still exist annoying gaps in logic which the author has overlooked. Now this here may be more of an example of nitpicking, but that's just part of who I am and I wouldn't be complaining so much if I didn't know that I'm not the only fantasy reader out there who finds this mildly annoying.
A good (or bad) example of this would be the magic in Eragon. As much as I love to complain about the Inheritance Cycle, I don't think Paolini's magic system is all that bad. To be honest, reading Eragon when I was younger has had an influence on the creation of my own magic system, more so than I'm totally comfortable admitting. However, the one major design flaw I see in it is the use of energy in magic. On the surface, it seems reasonable enough: performing a task with magic takes the exact amount of energy it would to perform it manually. But then you start running into problems with energy expenditure, especially concerning acts which are impossible without magic, like creating giant fireballs or putting up magical force fields. How is anyone supposed to know how much energy something that can only be done magically would take without magic? And what about the huge amounts of energy that creating fire would take? Is it equal to lighting a fire with a match, or equal to the amount of chemical energy in the body which would need to be converted into heat energy to create fire? Is there a special form of magical energy that exist which magic user utilize? There doesn't seem to be.
And then of course we have examples which show that the absolutist assertion that magic must be exactly equal in energy expenditure as manual labor is just plain illogical. At one point, Eragon lifts a sphere of water out of a stream. Is this equal to the energy he would have used lifting that same amount of water in a bucket? Or would doing it manually that way cost more energy because he'd be lifting the weight of the bucket AND the water, as opposed to just the water? Is he using the amount of energy that it would take to lift the water with his hands, which would be impossible? How about the energy it would take to remove the water from the stream via splashing? Does doing it magically cost more energy because lifting a sphere of water in any other way would be impossible because people can't waterbend? And don't even get me started on the silliness that is the Ancient Language...
And then we have the cases in which the pseudo-science just flat out kills the magic. Oh yes, you know I couldn't end this rant without mentioning the fuckery that is the Star Wars prequels and midochlorians. That single line has got to be one of the worst ideas in movie history, and it made a mockery of all the things that had made the Force magical. What makes these microscopic bacteria so special that they allow living things to tap into this mystical energy field? What purpose do they serve to the story except to show that whoever just so happens to have the most midichlorians must somehow be the "chosen one"? And how are they counting them, anyway? Is it the total number in the body, or how many are in each cell? If the second one, does George Lucas have any concept of how tiny they would have to be to have a lot of them living in individual cells? Does concentration matter, or only number? If you bleed, do you lose midichlorians? Can you gain more back? Do they reproduce? WHAT THE FUCK ARE THEY AND WHY DO THEY EXIST?!!!!
Bottom line, don't be stupid. Consider this a PSA to all the fantasy writers out there: if something about your magic needs to be explained, you gotta know what the fuck you're talking about.
Satireknight's sporking of The Twilight Saga Illustrated Guide