I just found out that there’s a library in Paris that’s focused on Asian books that has over 600 books in Korean! And I’m talking mostly novels, with a couple picture books and webtoons. Shipping in France is very cheap (5€ to 7€), although it’s probably a lot more expensive for international shipping.
It’s called the Librairie Le Phénix . I put the link directly to the page with the fictions/nonfictions written in Korean, but there’s also some books specifically for Korean learners here.
(As an additional note, this bookstore is actually more focused on Chinese, so if you’re looking for Chinese books, they have over 2500 books in Chinese. They also have a respectable selection for Japanese and some other Asian languages as well.)