This one is just phenomenally great:
amazon.com/The-Anubis-Gates-Tim-Powers/dp/0441023827/
I can pretty much guarantee that you would become totally absorbed in this book!
I strongly second anything by Tim Powers, great fantasy writer (and a Catholic).
Have you read C.S. Lewis’s other fantasy series? (“Perelandra,” “Out of the Silent Planet,” and “That Hideous Strength”) His "The Great Divorce is more of a parable than fantasy (it’s about Heaven, Hell, and possibly Purgatory) but you’d probably enjoy it.
I’d also recommend:
Ray Bradbury - “Something Wicked This Way Comes” Classic fantasy about a mysterious, evil carnival that comes to a small Missouri town, through the eyes of two young boys.
Poul Anderson - “Operation Chaos” - In an alternative Earth where magic has developed more than science, we follow a likable Czech-American werewolf and his witch wife from fighting in World War II (fought in their world not against the Nazis, but an Islamic sect that is closer to ISIS) into the present time as they battle against elementals, dragons, djinnis, and finally the forces of Hell itself.
You might also like Anderson’s “Three Hearts and Three Lions,” about an American soldier fighting with the Danish underground who is knocked out in combat and awakens in a world where Charlemagne still rules amid a world of knights, dragons, and wizards, and his “Three Hearts and Three Lions” set in the elfland of old Norse legend. Both were published back in the 1950s and were very influential on modern fantasy authors.
Gene Wolfe - “Knight” and “Wizard” (published in a compendium as “The Wizard Knight”) - a young teen is transported to a world of knights and dragons, magically aged to an adult. Great adventure story with some deep stuff going on behind it.
Michael Flynn - “Eifelhelm” more SF than Fantasy, but great. An alien ship crash lands in Germany in 1349, and a Catholic priest makes contact.
Jerry Pournelle and Larry Niven’s “Inferno” is quite good. A Sci-Fi writer dies by accident and wakes up in Hell, exactly as described by Dante. With the help of a mysterious stranger, he tries to escape. Just as Dante used his description of Hell to critique the famous people of his time, so do the authors. There’s a good sequel, too.