First, they can give the impression that the story you're about the read has a scope that needs a map. Have you ever read a book, and then struggled to find where the heck on the map it takes place, only to discover that it all happens on the remote corner? Why does this story need a map? Far from impressing readers with the level of world-building, a map in this case sets up false expectations, and ends up doing more harm than good.
Secondly, they encourage some writers to name-drop far-off locations in the text, with the knowledge that the readers have a map, and perhaps with the expectation they will refer to it. Again, this is doing the story a disservice. Do we really want the reader to stop reading and consult a map?
Third, they give the impression that the reader needs to have a broad knowledge of the setting. Usually, this involves a number of kingdoms and their relationship to each other. If the story is on a geopolitical scale, maybe this will be helpful. But in the real world, very, very few people can generate anything like an accurate map of even their own country and its immediate neighbors. Having a map may give the characters hyper-accurate reckoning skills when thinking about the distances between places. The writer may, even subconsciously, always use the proper distances between places, thinking that having the characters be wrong when they talk to each other (or plan for travel) will be seen as a mistake on their part. In truth, people think about travel in terms of time, not distance. People will usually say how far away the grocery store is in terms of travel times. Places are five minutes away, not three miles. So writing a story with a map means you have to think about travel times, not distances, and that's sometimes hard to remember. Have you ever read a story where the characters casually mention the exact distance to a destination, but never the travel time they expect? Yeah, me too, and that's just not the way it works, especially in a fantasy setting, where foot travel is usually the order of the day.
So, is it all downside, having a map? Obviously not!
A good map in a fantasy story must do these things in order to be beneficial:
First, it must be clearly drawn. Blurry rendering, tiny lettering, obscure fonts, or crowded landscapes all make your map a chore to peruse.
Second, the map must be relevant to the story. It must have useful locations marked on it, which means it must be of a useful scale. Giving a world map for a story that takes place in a single city might not be so useful. The locations given can even include locations from the story itself that wouldn't be marked on most maps, such as an important ford in a river, a character's home, or the route taken in the text.
Third, maps need to relate some information that is not in the story, to put the events into context. Sometimes, just knowing the characters are starting out on the west coast of a place, and travelling east, makes reading the story easier, but maps can help supply the reasoning for jogging to the south for a while (like mountains, or some other hazard). I've read very popular books whose maps showed a basically empty landscape with just a few towns and other locations marked, and lo and behold, those were the places we visited in the story. No other locations were marked, nor mentioned in the novel, making the landscape seem entirely empty save for those few places. Without a map, this would not have been an issue.
Lastly, maps must be based in reality, even for fantasy worlds. Generally, landscapes are shaped by different natural processes, and cities develop and grow in other ways. Unless your landscape is entirely fantastical, and your cities completely artificial, you need to be aware of these patterns, so that your maps will read as being a real place. Having coastlines and mountains and rivers all mashed together without reason, cities dotting the landscape in no particular place, these sorts of maps do a setting no good at all. They falsify rather than reinforce.
I'll be talking more about how to create realistic fantasy maps in a later post, so stay tuned!
