Pablo Neruda — Start with Twenty Love Poems and a Song of Despair (1924) or the Canto General (1950). The poems ground themselves in Chilean landscapes, and reading them before visiting the Sierra Nevada or the Atacama changes how you see those places. After visiting La Chascona, try Memoirs (also translated as I Confess That I Have Lived), his autobiography — lush, opinionated, and full of the extraordinary life he led.
Isabel Allende — The House of the Spirits (1982), her debut novel, is the essential introduction to 20th-century Chilean political history as seen through the lives of three generations of women. It fictionalises the Allende/Pinochet era without pretending to documentary precision, which is why it works.
Roberto Bolaño — The Savage Detectives (1998) is nominally Mexican, but Bolaño was Chilean and Santiago marks the starting point of his obsessions. His novel Nocturno de Chile (2000) deals directly with the dictatorship years and the complicity of Chile's intellectual class with the Pinochet regime.
Ariel Dorfman — Death and the Maiden (1990), a play rather than a novel, is the best dramatic work to come out of the dictatorship: three characters, an isolated house, and the question of whether the man one character believes tortured her is actually who she thinks he is.