Nabokov's definition of a major writer

"There are three points of view from which a writer can be considered: he may be considered as a storyteller, as a teacher, and as an enchanter. A major writer combines these three—storyteller, teacher, enchanter—but it is the enchanter in him that predominates and makes him a major writer.
To the storyteller we turn for entertainment, for mental excitement of the simplest kind, for emotional participation, for the pleasure of traveling in some remote region in space or time. A slightly different though not necessarily higher mind looks for the teacher in the writer. Propagandist, moralist, prophet — this is the rising sequence. We may go to the teacher not only for moral education but also for direct knowledge, for simple facts… Finally, and above all, a great writer is always a great enchanter, and it is here that we come to the really exciting part when we try to grasp the individual magic of his genius and to study the style, the imagery, the pattern of his novels or poems.
The three facets of the great writer — magic, story, lesson — are prone to blend in one impression of unified and unique radiance, since the magic of art may be present in the very bones of the story, in the very marrow of thought. There are masterpieces of dry, limpid, organized thought which provoke in us an artistic quiver quite as strongly as a novel like Mansfield Park does or as any rich flow of Dickensian sensual imagery. It seems to me that a good formula to test the quality of a novel is, in the long run, a merging of the precision of poetry and the intuition of science. In order to bask in that magic a wise reader reads the book of genius not with his heart, not so much with his brain, but with his spine. It is there that occurs the telltale tingle even though we must keep a little aloof, a little detached when reading. Then with a pleasure which is both sensual and intellectual we shall watch the artist build his castle of cards and watch the castle of cards become a castle of beautiful steel and glass." 
(Vladimir Nabokov)