I still have this really clear memory from college of wrestling with 'Moby-Dick' over a whole summer. At first I just wanted to get through it, but somewhere around the middle, with all those digressions about whale biology and rope textures, it clicked. That was his influence right there, long before I knew the term. He wasn't just telling a story; he was constructing a whole cosmology around a sailing ship. Later American writers, like the postmodernists, totally ran with that idea of the novel as an encyclopedia, a container for every thought a person could have about a subject. He gave permission for fiction to be messy, ambitious, and structurally wild in a way that the neat, moral tales of his time just weren't.
His influence feels indirect but massive, like a tectonic plate shifting under everything written after. You see it in the way someone like Thomas Pynchon or David Foster Wallace builds these immense, layered worlds where the plot is almost secondary to the sheer density of ideas. Melville proved that American literature could be philosophically weighty and stylistically complex, that it could stare into the abyss of nature, God, and obsession without needing to provide a tidy lesson. He moved the novel from the parlor to the vast, terrifying ocean.