For me:
Dune, the entire collection.
The Alien books (including alien vs predator.)
All my sins remembered. A good book about an intergalactic assassin recalling how he got to where he was.
Phillip K. Dick, We can remember it wholesale (what was turned into Total Recall.) Do androids dream of electric sheep (blade runner)
Most of Asimov's works, mainly The Last Question.
Bradbury, ofc A sound of thunder, something wicked this way comes, there will come soft rains (saddest short story I feel he has written.) Fahrenheit 451.
George Orwell 1984
Those are some of my library. Right now, I am into light novels based on anime I watch when I can find the time. or alternate history, like Turtledove's altered history take on ww2, every event the same, but with magic, and all.
Also H.G. Wells.
Also not a sci fi book per se, but I also have Gieger's artbook I cannot spell his name right for the love of me. He is the artist who inspired the xenomorphs from Alien/s