Emotional books that are bittersweet

Exactly what the title says.

Bonus if it is/has:

• sad/ambiguous ending

•a classic

•not very long (400 pg max)

•main character with tragic backstory

If these do not apply please recommend anyways!!! :))
Some stories I’ve liked for reference:
Of Mice and Men, The Catcher in the Rye, A Little Life, Banana Fish(manga but I had to include it), the Song of Achilles