Doing the same here. You can still find most of them used on amazon. Many of them are discards from US libraries. You can usually get them for a couple of bucks.

My biggest surprise was Rogue Moon (Hugo 1961). Incredible ending, up there with Man in the High Castle (Hugo 1963).

I agree with the "fascinating tour" part. The earlier books (from the 50s and 60s) where clearly more optimistic and more realistic at the same time. The human nature was captured more accurately I believe, most of the heros were actually anti-heroes. But the human capabilities were clearly over evaluated and the social interaction a little simplistic. Also, its funny to read books were martians were still a plausible thing (Protector Hugo 1973).

If I have an advice to give you it's: don't limit yourself to the 90s onward. You are missing on gems like Rendez-vous with Rama (Hugo 1974) or Forever War (Hugo 1976).

I really enjoyed the books from the 50's before people really started thinking of computers, plastics, composite materials and so on.

They would be flying around in their spaceships using slide rulers to calculate everything, wearing their fur-lined space suits etc.

"The earlier books (from the 50s and 60s) where clearly more optimistic", I am not that sure, "Fahrenheit 451" by Ray Bradbury (1953) is far from optimistic. It didn't get Hugo at its time, though, but got "retro" Hugo later on (2004).

But maybe you are right, it didn't get Hugo because it was too pessimistic, unfortunately, this one book gets more and more up to date with its predictions...

I have a complete-but-one set of the Gardner Dozois-edited Best New SF for much the same reason. You can pinpoint the exact year everyone realised networks were going to be big, or when turgid Dune-influenced 70s SF got replaced with fast, nimble cyberpunk.