"Favorite" is a relative term; my favorite books are the ones I remember best or have read the most times. Favorite novel: Moby-Dick. Favorite theology: The City of God. Favorite poem: The Rime of the Ancient Mariner. Everything else is just stuff I like. I read as a Christian, and compare everything to the Gospel of Christ.
I don't think books should be read just because they're "great literature." I understand the argument, but greatness belongs to the Lord, and human systems of value are famously flawed. We read to understand the world God made, and thereby to give Him glory. Without that, much study is wearying to the bones and will make you shortsighted.