I’m not much of a reader of fiction, but (depending on your age) my recommendations (and some of my favorites) would be these, all very, very readable:
“One Day in the Life of Ivan Denisovich” by A.S. Solzhenitsyn. Not very long at all, extremely readable and engaging. It chronicles one day in the life of a Soviet prisoner in the Gulag. One might think it a miserable downer of a read, but it actually isn’t. Tells a person a lot about humanity, human dignity and human resilience. A major, major modern classic. Won the Nobel Prize.
“A Canticle for Leibowitz” by Walter Miller. Probably hard to find except perhaps on Ebay. Very Catholic, very, very good analysis of how human longing for paradise can go so right or so wrong. Interesting, readable, and moves right along.
“Odd Thomas” by Dean Koontz. Very Catholic in morality, but in a science-fiction/ghost story sort of way. Amusing at times, disturbing at times. Spooky, but fun. About a guy who can see ghosts of people and other spirits, including Elvis (who is sort of in purgatory) and about how human vanity can go very wrong.