Well, perhaps one is Tolkien’s world, where magic seems to be there, is somewhat explained (some creatures possess it, such as the Wizards and elves, while others, such as Hobbits and Man, do not), but doesn’t seem to follow any set rule (there isn’t any particular set limit to what the Wizards can do, where the power the artifacts have such as the elven cloaks and palanti, etc). Certainly Tolkien had notes on these things (at least where the artifacts originated), but it is not apparent to the reader (nor does it need to be), and the artifacts could have worked just as well without any origin notes needed for them.

I think where the real confusion lies is when you are not consistent with magic (a blast of fire lights a simple candle, and then on the next page obliterates a wall), or magic isn’t used in a logical fashion (such as using/not using magic in a certain way to advance the plot, where otherwise it would/would not be used).

Even with that, magic is still generally mysterious enough that even major inconsistencies can later be explained in some manner. That’s the beauty of magic.

Lukahn’s last blog post was Fantays World Building, pt 3