One of the things that makes a fantasy novel so fascinating is the world that is created by the author. Normally this is a world that doesn’t exist, except in the author’s mind, or a variation on the Earth we know. The only problem with this is that the Reader may sometimes have a difficult time figuring out where the characters are, geographically speaking, at any one point in the novel.
This is why Maps are such a great addition to a fantasy story. You, the Reader, can easily orient yourself to the characters’ locations and the general geography as a whole.