I think the reason Philip K Dick is still the predominant SF writer of the last century is, he was the only one who foresaw a future where everything would be boring, inconvenient and dehumanising, and where the only way you can win is to somehow refuse to give up your humanity.
Here I'd say 1984 and Brave New World, but the mainstream took them and almost ignored their SFnal natures, whereas Dick and Butler are still viewed as SF writers by people who know them.