Check out Sophia Institute Press (www.sophiainstitute.com) for a number of fabulous Catholic fiction and non-fiction books. My nieces and nephews are all hooked on the "John Paul II High" series (geared toward teens, but I liked them, too!)
Any of Louis de Wohl's novels on the saints... start with "The Spear"!
Marcus Grodi (of Coming Home Network) wrote a novel entitled "How Firm a Foundation" which is excellent!
For a classic: "A Tree Grows in Brooklyn" by Betty Smith (my all-time favorite book!)
More secular novels:
Mary Higgins Clark's romantic suspense novels
Aimee and David Thurlo's "Sister Agatha" mystery series
James Patterson's "Detective Michael Bennett" series (WARNING: very violent and gritty, but with an unmistakable Catholic flavor!)