I have read a few S-Tier fantasy books but never came across an S-Tier science fiction book.

I start to believe there's no such thing as an S-Tier book in that genre.

Used to build @kiwi | https://macbudkowski.com/

Fahrenheit 451
1984
Brave new world 
A scanner darkly

Scanner darkly is really good if you like those, they actually made it into one of my favorite sci fi movies too

Scanner darkly is really good if you like those, they actually made it into one of my favorite sci fi movies too 

https://youtu.be/hkjDUERgCQw?si=WkMnD5lJxr8jmkH0

Read first 3, haven't considered them scifi, but I think you're right by putting them in that category. 

So 1984 and Brave New World would make it to S-Tier!