Recently, my father mentioned to me that he had picked up a book in the library discards which focused on the history of electrical inventions and inventors in the 19th and early 20th centuries. He said that as far as the historical facts went, the book was okay, but when the author came to actually talk about electricity, it was clear that he knew nothing, and my father found it so infuriating as to almost make him want to throw the book across the room. He didn’t throw the book, though; he’s got too much respect for the written word to do that.
This got me thinking about some of the things that will make me stop reading a book, and one of the top ones is being able to tell that the author knows nothing about the subject at hand. It’s important to know what you’re talking about, even if you’re making things up wholesale.
Urban fantasy is not science fiction–you’re unlikely to find particle accelerators (unless you’re reading a story set at CERN or something), warp drives, cyborgs, or any other science fiction staples–but this doesn’t mean that you aren’t going to run across things that authors need to research. Guns are a good example. How many times have you played “count the shells” in an action movie or a fight scene in a book? Not everyone will know that a Colt 1911 holds seven .45 ACP rounds in a magazine (plus one in the chamber), but if your character uses a 1911 and fires nine or more rounds without reloading, someone is going to notice.
Guns are only one example, but they’re an example that I think is especially relevant to urban fantasy, considering the genre’s preponderance for leather-clad women with heavy firepower. If you’re going to be specific about a character using a specific firearm, make sure you know as much as possible about it. Likewise, make sure you know the specifics of the car that your character drives. You don’t need to put everything you know about a specific piece of kit on the page, but you need to know that information.
For those things that you make up, a good way to establish yourself as an expert is to explain something very simple. If you can explain something that readers know, then they’ll not look as closely at the things that they don’t know.
If you feel that doing such research is nothing more than a chore, then cut back on the technical details, but remember that if you have fewer details, your readers are less likely to be immersed in your stories. You need to strike the right balance between too many and too few details in your fiction, whatever the subject matter.