This is a distinction to which I often return. I think most people intuitively can sense the difference between “great literature” and a “great read.” But what is the difference? For example, a book like the Da Vinci Code or — yes, I'll admit to reading it — Twilight is engrossing, with interesting characters. Who doesn't want Robert Langdon to survive as the evil Teacher tries to kill him? Who is unsympathetic to Edward Cullen as he struggles with being a “cold one”?
To the extent that we can empathize with the characters, and their plights can cause catharsis (I think more likely in the case of Cullen than Langdon), they mimic great literature. Much of what makes Hamlet or the Oresteia great revolves around the ability of these works to connect with our core being and make us feel the sorrow and joy the characters feel.
But, I would not group Twilight or the Da Vinci Code in the realm of great literature. Simply the realm of a “great read.” Why is that? What is the essential substance of literature?
Part of it is surely the test of time. Will anyone remember Bella Swan in two millennia as people still remember Agamemnon today? I'm dubious. Part of becoming literature is passing the judgment of cultures and times other than our own.
Yet if we say that literature must stand the test of time, precisely how long of time? Surely we must not say master works such as T.S. Eliot's the Waste Land are still awaiting judgment. When did it become literature or was it always literature?
The best answer, I suspect, is to view time's vote not as the deciding one, but as a natural consequence of another characteristic of literature. This characteristic is that literature frequently defines or alters the framework within which it operates. That is, Shakespeare's plays changed the very essence of drama; Dan Brown has not manipulated the genre of the action/puzzler novel to any great degree. But, agreeing with Eliot's discussion of literature in “Tradition and the Individual Talent,” literature must not be purely “change,” literature must also be intelligible. (Hence why I continue to mock Samuel Beckett's Waiting for Godot — it does change the fabric drama, arguably, but hardly in a way intelligible to drama as drama.)
Intelligible alteration of genre and framework. That is essential to what makes a great read great literature, but it is merely a part, not the whole of that which defines literature as literature.