Fabiola, or, the Church of the Catacombs, by Cardinal Wiseman (1886), is a historical fiction that was written with the intention of being a pious, lawful recreation/relaxation for Catholics. Featured are some drawings from the actual catacombs themselves!
With his knowledge of the early Church and the martyrs of that age, he weaves together the lives of different saints, and creates a story out of it. The main themes are sacrifice, perseverance, conversion, and repentance. Fabiola is the main character, who is a Roman, pagan noblewoman, with an intelligent mind that is disposed to receiving the truth. One of her slaves is a Christian, unbeknownst to her.
St. Agnes is featured as being a close friend of Fabiola, St. Sebastian's virtues are admired by the pagan Fabiola, without her knowing the source of it (Christianity), and so on.
It is one of the most beautiful books I have ever read, Cardinal Wiseman could have made a career being a novelist, in my humble opinion. I finished it in less than a week, it was difficult to put it down.
I wish I could describe more, but I would be spoiling it!
It's available here online: https://archive.org/details/fabiola00wise/page/n7/mode/2up
I have the reprint from Ave Maris Stella Publishing on Amazon, it is very high quality.