Mars was alright. I had a lot of trouble with one of the books. Took almost a year to read because it felt like there was nothing but political infighting in it.

Foundation was actually what got me started on the "future histories" kick. The civilization is a more fleshed-out character than any human in the story. But I was eleven and didn't read any further than the original trilogy.

My favorite golden-age sci-fi would probably be Heinlein's "The Past Through Tomorrow" collection. The parallels between Elon Musk and D. D. Harriman are amusing.