I write mainly horror and fantasy, so my work is full of things that either don’t exist, can’t exist, or most people wouldn’t accept existing. Demons, guardian spirits, soul transference, sympathetic magic, mind reading, ghosts and were-kittens have all appeared in manuscripts I have written or I’m currently writing. In exploring these topics, there are two levels of acceptance I need to get from the reader.
Whatever genre a story falls under, it is important to get the reader to accept all aspects of it from the setting to the characters and their motivations. If the reader stops accepting what they are being presented, then they can get confused or frustrated with the book and in the worst case, they’ll put it down and not pick it up again.
But in my opinion, there’s a difference between being realistic, and being believable.
Realism applies to things that exist in the real world. Even in fantasy, realism is important. Normal people cannot just pick up a sword and become world-class fighters. Horses have limits in how much they can carry and how far they can run. Different weapons have different purposes, skills required to use them, and effects on armour. If you have no magical healing system, injury and infection are major risks to your characters. Some things will only be criticized up by the very nit-picky readers, and most will forgive a good story minor transgressions, but a bit of research can go a long way to making the story realistic.
But what if you do have a magical healing system? What if travellers watch the sky for dragons, or the undead stalk abandoned supermarkets? What if there are aspects of you book that will never be realistic? Given the number of fantasy books published, not to mention all the other genres that aren’t fully realistic, there isn’t a problem in getting readers to pick them up. If you’re anything like me, I prefer to be taken away from reality as much as possible.
It still has to be believable though. I still have to accept whatever wild wonderful ideas you throw at me in a book. Mostly it comes down to consistency. When you set up the rules of your world, you need to keep to them. If you tell me dragons need to eat a hundred sheep a day, then send your dragon riders into a desolate wasteland for a week, I’m going to expect there to be some negative effects on their mounts. If your super prototype giant robot defeats all adversaries without so much as a scratch until badly damaged by a tank simply because the plot requires it to fail at that point, I’m going to rage.
So, flying, fire-breathing lizards are not realistic. If you tell me you saw one flying over Bristol, I’m going to wonder what you’ve been smoking. But if you build the world right, I’ll happily dive into a fictional story and consider them no less believable than horses or turnips.