Greatest Science fiction Novels of all-time that I should read?

I haven’t read any Sci-fi novels yet, but I’d like to.

What are some Sci-fi Novels that are absolute essentials?

Sci-fi of any kind is acceptable: Adventure, Hard Sci-fi, Sci-fi Warfare, Post-Apocalyptic, Dystopian, Cosmic Horror, Libertarian, Alternative History/RetroFuturism, Cyberpunk, Space, Space Epic, Feminist, Conservative, Libtertarian, Leftwing, Body Horror, Extraterrestrial, Biopunk, etc.