I would have to agree with a well-educated adult reading Shakespeare. He is well deserving of his reputation.
In addition to The Bard:
2. Les Misérables - Victor Hugo
3. The Brothers Karamazov - Fyodor Dostoyevsky
4. The Republic - Plato
5. The Adventures of Huckleberry Finn by Mark Twain
6. Anna Karenina by Leo Tolstoy (even though I, myself, prefer The Kingdom of God is Within You)
7. Utopia - Sir Thomas Moore
8. Beowulf - Author unknown
9. Paradise Lost by John Milton
10. Damien - Hermann Hesse