Over two years ago, we published a version of this list featuring 50 books. But why stop at 50? Now, as part of our latest Summer Fiction Week, we’ve cast a wider net and expanded the list to 75 titles. Choosing the 75 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.”

Now, in ranked order, here are the best science fiction books of all time.