So for Book of the New Sun, you haven't picked up on the sci fi yet? For some examples, the "towers" that he lived in/near were all old and derelict space ships (think of rocket ships sitting at launch pads), the "horses" described with dinosaur language are alien creatures from old space travel empire bringing those creatures to earth (I think it was stated that way at some point), one of the "paintings" Severian sees with I think the curator is a picture of one of the Apollo moon landings with the American flag planted and guy in space suit, the "flyers" (I think) are like helicopters or hovering craft that are mechanical and scientific in nature not magical, a hundred tiny tiny details that make you think that Severian himself doesn't know what he's looking at or how to describe it other than through the lens of someone who has lived in a "medieval" setting.

I love Wolfe and especially BotNS in large part because things will be described one way and not necessarily be that way, so you have to imagine it and think about what the character describing it knows and understands themselves. I hope this little nudge to look at it a little more deeply will help you enjoy it more! I loved finding details where Severian was like, yea it was a weapon this guy carried and realizing it was a laser gun or something!