For me it is Foundation series because I like it's themes and how they are presented, I really like some characters like Mule and Hari Seldon and it is very interesting to read.
I recently read Artemis by Andy Weir, but the protagonist had so much teenage angst that it was difficult to finish despite its short length. I'll have to try one of his more popular books instead.
I feel like you’d really enjoy House of Suns by Alastair Reynolds. One of the most “lived-in” feeling worlds I’ve encountered since Hyperion. I’m reading Pushing Ice now and haven’t read any of Revelation Space yet, but I’m planning on it.
I don't see many people recommending Ancillary Justice, but really enjoyed the series. I thought it was a pretty light read as far as Sci-fi goes, but it ticked all the right boxes for me.
I wouldn't call AJ a light read, just because you spend so much time wrapping your brain around what the narrator is doing and the cultures are so deliberately weird. All the more rewarding for it though imo.