Anna Karenina
Anna Karenina, a beautiful, intelligent woman trapped in a passionless marriage to a cold, high-ranking official, falls into a consuming affair with the dashing cavalry officer Count Vronsky, a choice that will unravel her standing in St. Petersburg society and her own sense of self. Running alongside her tragedy is the quieter, more redemptive story of Konstantin Levin, a restless landowner searching for meaning in faith, farm work, and his marriage to the young Kitty Shcherbatskaya. Tolstoy braids the two arcs into a sweeping portrait of Russian aristocratic life, setting Anna's spiral toward ruin against Levin's slow climb toward peace. It's a novel about desire, hypocrisy, and the crushing weight of social judgment, building to one of the most famous endings in literature.
You've already gone the distance with Dostoevsky, so Tolstoy is the natural next climb: the same command of interior life, but a wider social canvas and a more patient, accumulating structure. Anna Karenina rewards the kind of stamina you bring to a long run — it's slow to open, then never lets go once Anna's affair and Levin's parallel search for meaning start pulling against each other. It's the book people mean when they say "the realist novel at its peak," and it will sharpen how you read everything else on this list. Block out real time for it; this isn't one to skim between other books.