Love story in a novel

Can anyone recommend me a book that has:
– a straight love story
– no affairs (by the main characters)
– a good plot outside of the romance

I quite like books with enemies-to-lovers or one person falling for the other earlier in the story. My favourite book is Pride and Prejudice, if that gives you the vibe, and I just finished North and South. I like to read classics but I'm open-minded. Thanks so much!