Quietly sad books

It's my favorite type of books, but it's difficult to figure out which one would hit the right balance. Subtlety is important. Plot isn't. It doesn't have to be literary fiction, but I haven't come across too many genre book with introspection and the right tone. They are usually focused on the plot.

A Few examples of books that I liked that fit the description:

• Heaven and Hell by Jon Kalman Stefansson,
• Butcher's Crossing and Stoner by John Williams,
• Memoirs of Hadrian by Marguerite Yourcenar,
• Giovanni’s Room by James Baldwin,
• All Quiet on the Western Front by Erich Maria Remarque,
• Remains of the Day by Kazuo Ishiguro,
• Steppenwolf by Hermann Hesse,
• Immortality by Milan Kundera,
• Nausea by Jean Paul Sartre,
• Norwegian Wood by Haruki Murakami,
• Out Stealing Horses by Per Petterson,
• Dune Messiah by Frank Herbert,
• Einstein’s Dreams by Alan Lightman,
• Interview with the Vampire (first book) by Anne Rice,
• The Terror by Dan Simmons,
• Among Others by Jo Walton

Examples of books I didn't like:

• The Fault in Our Stars by John Green,
• A Thousand Splendid Suns, The Kite Runner by Khaleed Hosseini,
• On Earth We're Briefly Gorgeous by Ocean Voung

Fault in Our Stars and Hosseini's book were too much on the nose in their central theme for my taste. I know Hosseini is a popular author, but he is very unsubtle in his writing in my opinion. I've seen Ocean Voung recommended a lot, but I just couldn't connect with the book, writing felt too constructed and artificial. Could be that I wasn't in the right mood for it. I might try again in the future.

Hope you can help.