Suggest me a book that has a romance story in the background

I’m looking for books that have a main story but the characters just so happen to fall in love on the side. I love anything horror/thriller, fantasy, sci-fi, and historical fiction. My only request is for you to not recommend books that are set in our current time period, like if an iPhone or an email is mentioned in the book I don’t want it, they feel too close to my own life haha.