C. J. Cherryh
The field's most rigorous builder of alien minds and interstellar economics.
Anthropological SF
Science fiction built around cultures, languages and societies as rigorously imagined as any starship drive.
The authors (2)
Ursula K. Le Guin
The genre's most honoured writer and its moral centre of gravity: the standard demonstration that SF and fantasy can do everything literature does, plus things only they can.
Essential books, oldest first (9)
The Left Hand of Darkness
Hugo and Nebula winner, the founding masterpiece of feminist SF, and a permanent fixture at the top of all-time lists.
Downward to the Earth
Widely rated among the finest SF novels about colonialism; its sacramental aliens and penitent imperialist predate (and arguably outclass) several famous successors, Avatar included.
The Fifth Head of Cerberus
Wolfe's first masterpiece and the standard demonstration text for unreliable narration in SF; its post-colonial hall of mirrors anticipated discussions the field took decades to catch up with.
The Dispossessed
Hugo, Nebula and Locus winner; the standard against which all political SF is measured, taught in politics departments as readily as literature ones.
Downbelow Station
Hugo winner (1982) and the cornerstone of the Alliance-Union future history; its station-level realism is the acknowledged foundation for The Expanse school of space opera.
Helliconia Spring
BSFA and Campbell Memorial Award winner; the trilogy stands as British SF's grandest worldbuilding project and a clear influence on later planetary epics from Robinson's Mars onward.
Speaker for the Dead
Swept the Hugo and Nebula the year after Ender's Game did — an unrepeated double — and established the 'ramen/varelse' hierarchy of alienness that xeno-ethics discussions in the genre still borrow.
Cyteen
Hugo winner (1989) and a regular pick for the best SF novel about cloning ever written; its psychogenesis arguments anticipate decades of behavioural-genetics debate.
Foreigner
The launch of SF's longest-running first-contact study (twenty-plus volumes and counting) and the genre's most sustained meditation on translation as survival.