Clarke, Niven, and Heinlein for me. The original _Rendezvous with Rama _inspires awe in me every time. Stranger in a Strange Land is beautiful. The Known Space (Ring world) books are among my favorites. I’m also very fond of Ian Bank’s The Culture , though they are from this millennium and maybe out of scope for this conversation!
I have and love Burroughs’ John Carter of Mars, Zelazny’s Amber, and Castle Perilous by John De Chancie. I’ve just started collecting E. E. “Doc” Smith. I’m slowly adding to my Ursula Leguin and Lester Del Ray shelves.
And I really can’t resist buying old yellow books with ridiculous titles like “_Mutiny in Space” , “assault on the gods” , or “The shattered stars”. _ Bonus Points for awesome spaceships on the cover. I’ll buy those any day without any idea of the author or story.