Maybe Greeley's novels weren't pornographic, but they're not literature. A reviewer from the Chicago Sun-Times said that "Cardinal Sins is enough to give trash a bad name".  Here are some good Catholic novels that I've read:

Diary of a Country Priest – Georges Bernanos
Silence – Shusaku Endo
The Cypresses Believe in God – Jose Maria Gironella
Brideshead Revisited – Evelyn Waugh
Viper’s Tangle – Francois Mauriac
The Samurai – Shusaku Endo
Mouchette – Georges Bernanos
Under Satan’s Sun – George Bernanos
The Unbroken Heart – Robert Speaight
The Mandelbaum Gate – Muriel Spark
Thérèse Desqueyroux – François Mauriac
Woman of the Pharisees – François Mauriac
Postcards From the Volcano – Lucy Beckett
Love in the Ruins – Walker Percy
Morte D’Urban – J.F. Powers
The Wheat That Springeth Green – J.F. Powers
An Instance of the Fingerpost – Iain Pears
The Dry Wood – Caryll Houselander
Lying Awake – Mark Salzman
The Island of the World – Michael D. O’Brien
Mariette in Ecstasy – Ron Hansen