Of all his works, in my opinion, none are more highly regarded as H.G. Wells' 1898 novel The War of the Worlds. This novel is one of the few early works of science fiction that holds up well to this day and is one of the “greats” of the alien invasion sub-genre.
Richard Matheson's 1954 novella, I Am Legend remains perhaps his best. It’s a book helped inspire new sub-genres in sci-fi and horror fiction. Yet, have real-world events toppled its status as a “great” of speculative fiction? Could it still be considered a “great”, despite this and its age?
Contemporary horror fiction can be defined by a singular name: Stephen King. With so many "greats" from him to select from, it's hard to only talk about one. Yet, his "great", in my opinion, is his 1977 The Shining.
Few books have polarised me like Frank Herbert’s Dune has. On one side, I love its worldbuilding and influence on science fiction. On the other hand, I’ve hated it for being a story that drags on when reading it.