Choosing the fifty best science fiction books of all time wasn’t easy, so to get the job done, we had to establish some guardrails. Though we assessed single installments as representatives of their series, we limited the list to one book per author. We also emphasized books that brought something new and innovative to the genre; to borrow a great sci-fi turn of phrase, books that “boldly go where no one has gone before.”

https://www.esquire.com/entertainment/books/g39358054/best-sci-fi-books/

Some of the books are part of series. Added the series as bonus prompts.