Previous posters have suggested some good authors and books. (Despite his increasing Mormon weirdness, I’ve always been a fan of Orson Scott Card.) I’ll offer up something less well-known. While I don’t think I would describe these as classics, I’d recommend the Deathworld trilogy by Harry Harrison. The main character is Jason dinAlt, a gambler who ends up dealing with inhabitants of a planet whose flora and fauna are trying to destroy them. In addition to being at least passably well-written, the three books play out the universal conflicts of man vs. nature, man vs. man, and man vs. himself. This isn’t classic stuff, but I’d wager you’ll find them interesting if for no other reason than the (presumably intentional) exploration of the Three Conflicts.