Which classic science fiction novel still holds up today?S

Sometimes you revisit a classic science fiction book that rocked your world years ago... and the letdown is like falling off a space elevator. Some beloved books just don't hold up. But sometimes? You read an old favorite, and it's even better than you remember. Which novels are just as great today as when they were published?

Share your pick below, and please include a cover picture! Thanks!

Top image: Chris Foss.