The world of Ascension is a giant mountain. A mountain so huge it takes a year to travel from its base to the summit. Maybe I'm a bit challenged in the 3D visualisation department, but I just can't picture what the map of a world mountain would look like. I can't even begin a rough sketch to show an artist how it might work. So I'm stuck with no map. (I'm open to offers though, if anyone thinks they can have a go or if they can show me some examples that work.)
What do readers think when they come across a fantasy novel without a map? I personally like well-drawn, detailed and thought-out maps, like the one depicting Tolkien's Middle Earth, but I think the simplistic scribbles that sometimes fill the opening pages of fantasy novels are actually a turn-off. They make the world seem smaller and more trivial. They diminish the story, rather than enhance it. They block the imagination. They suck out the magic.
My feeling is, if you're not going to do it properly, don't do it at all. The map should fit the setting and style of fantasy depicted in the work. A richly detailed epic requires a richly detailed map, and a pre-industrial or medieval-type world needs to have a map that appears hand-drawn and in a style that is in harmony with the world.
Assuming the map is of high quality and one that matches the work, should fantasy novels always have maps the same way they should always have characters and plots and magic? Are maps one of the integral aspects of a fantasy novel that define the genre?
If this is true, then I think it is only true of epic fantasies. Epic fantasies are large scale, intricately detailed, and usually involve travel, so a having a map fits the bill, suggesting a sweeping story on a grand scale.
However, outside of truly epic fantasy, how crucial is the map? Is it just a crutch because the words alone don't create the right pictures in the reader's mind? Is a failure of the writing?
I'm not sure if I have definitive answer to these questions, but a reader shouldn't have to refer to a map to make sense of the story. A map adds flavour, a feel to the novel, an interesting side-reference, but the reader should be orientated though the narrative alone. They shouldn't be dependent on the map.
So, I hope you forgive me for my mapless epic fantasy.