Indeed, Perelandra is good.

I’d probably have to say Dune.

Ender’s Game.

@Nimis
Also a good one, of course. I almost gave it an honorable mention.

Neuromancer by William Gibson
The Gap Series by Stephen Donaldson
Anything by Iain M Banks

The Amber series, by Zelazny. After Dune, of course. And any William Gibson. Not to forget the Honor Harrington series by Weber. Almost forgot Stranger in a Strange Land, and The Moon is a Harsh Mistress, by Heinlein. And….

Stranger in a Strange Land and Starship Troopers both by Heinlein.

Aid: If I were answering What is the best sci-fi novel?, I probably would have said Dune.
But for me personally, it’s always been Ender’s Game.

There are too many favorites to list them all, but I would have to say the very first science fiction book I read in elementary school that started me on a lifelong love affair with the genre.

Andre Norton’s Cat’s Eye

Mine would have to be City written by Clifford Simak. I read where Asimov said that Simak was his inspiration, and that his aim was to write in the same style. Having read Asimov’s Foundation Series years ago, and then more of his books since then, I read City just this year, and can definitely see Simak’s influence throughout all of the Asimov books that I have read.

As far as science fiction goes, it’s gotta be Ender’s Game. So many layers to that book; you can look at it superficially as a story about a kid that saves the world, or you can go deeper into his psyche, look at his siblings and their profound effect on the world populace, etc. etc. Fantastic book.

Not Ender’s Game, but the ones after that in the series. they’re wicked.

The Mote in God’s Eye, by Pournelle and Niven