There is often a grammatically correct way to use them, and a way that they work well in a story. Tolkien is a good example of this, where he had his own way of using language to get his story across. It worked well for him, but (imho) he isn't always entirely consistent in his usage and terminology. Unsurprising, as his work spanned many years and no doubt was spread over many thousands of pieces of paper with annotations, corrections and alterations. And no doubt his viewpoint on certain things in Middle-earth changed over that period.
It all worked out brilliantly well of course, but it would be interesting to see what a publisher would think of his story if it was submitted 'as is'. I wonder how many corrections and alteration he would be asked to make?