Deal Hudson's list of 100 Best Catholic Novels. The book, Silence , by Shusaku Endo, is, as described by wikipedia , "..... the story of a Jesuit missionary sent to 17th century Japan, who endured persecution in the time of Kakure Kirishitan ("Hidden Christians") that followed the defeat of the Shimabara Rebellion."
Graham Greene wrote that, "In my opinion one of the finest novels of our time". I'm not quite sure I'd go as far as Greene, but I will agree with Luke Reinsma, who wrote "Silence is an extraordinarily haunting novel."
In the novel, Endo addresses the question of mercy in both Christian and Bhuddist traditions as well as the issue of apostasy under the pressures of extreme torture.
Without giving away the ending - no spoilers here - I'd say Endo provides an interesting answer to the question, although I am not sure if his answer strictly follows Catholic teaching.
Silence is well worth one's time, but don't expect to feel comfortable reading it.