Suggest me a Sci-fi novel written in the 21st century that’s not in its core a Young Adult romance (preferably set in space).

Hey there,

I'm in a Sci-fi-phase right now and am reading classics from the last century (e.g Vonnegut, Farmer, LeGuin).

Recently I was in a huge book store and asked the subject matter bookseller in the book department for fantasy and sci-fi wether she could recommend a book, as described in the heading here, and she laughed and said that it's not easy right now bc the whole Young Adult romance hype has basically taken over the entire genre.

Do you have any suggestions?

Edit: I realize there are Star Wars, Star Trek, Warhammer 40k etc. novels out there, but I'm not interested in books that come from or are part of a franchise. If I want Star Wars, I'll watch a movie. (Not saying that the books are bad, it's just not what I'm looking for).