(Masked Chicken, you asked for a non-depressing post. This one's for you.)
Novelist Elizabeth Goudge said, though I seem not to be able to find the quotation now, that the quality of surprise is present in an encounter with all true beauty, and that if that surprise is not there, the beauty is counterfeit.
She was speaking of female beauty, physical beauty, but the same can be said of literary beauty and literary greatness.
A truly great work of literature should surprise you. It should surprise you the first time and time after time. "How can this be?" The double-take. The sudden or slowly growing realization that you are not dealing with just an ordinary book. It may come early in the work or only as it unfolds, perhaps at the very end. If there is not that element of amazement, in some cases an unanalyzable response, then I will go out on a limb and assert that either you are unusually dense or else you are not confronting a truly great work of art.
I have recently thought of this in connection with what is to my mind one of the great novels of Western literature--Chaim Potok's The Chosen.* It starts with a high school baseball game and a sports injury, but along about the time that Reuven Malter sits on the back porch and thinks about his time in the hospital, one begins to suspect the novelist's power. When Reuven sees and frees a struggling fly in a spider web, the suspicion becomes stronger. And by the time, much later in the novel, that he hears the world crying in the silence imposed between himself and his best friend, your eyes should be opening wide with that surprise--the genuine, unfeigned human response to artistic greatness.
What works of art--music, literature, sculpture--have invoked that response of surprise in you, readers?
*I do not mean similarly to endorse all of Potok's novels, the quality of which varies a great deal.