If you were to take a course on the Romance Novel in college, what books would you want to be on it and why?

Hi friends! I'm lucky enough to have found a professor who's willing to advise me for a romance novel special studies course next semester. I'm an avid romance reader who (partially due to the influence of this sub, thanks to all your fantastic discussion posts) has grown more and more interested in studying the genre from a more "academic" viewpoint. Now I might actually get to do it during school time, for credit, I'm beyond excited!

Looking at syllabi from other genre studies courses like science fiction classes offered at my school, I'd like part of the coursework to include the reading of a few historically and/or thematically significant romance novels. I'm looking for books that have had a huge impact on the romance genre (either because they challenged conventions, were wildly popular and led trends for a while after, or because they do something super interesting (what the Fated Mates gang would call "went hunting for big game") or exemplify a particular subgenre or trend). I'm looking for books that are rich enough to yield fruitful discussion, that may challenge my ideas of what romance is or isn't.

Obviously, there are a ton of romance novels out there that could all be studied for various reasons and I will only be able to cover a slice of them in a single semester course. I'm open to suggestions from wildly popular books that were published last year to super niche authors writing in the 1950s that I've never heard of. I'm definitely including an Alexis Hall book (perhaps an Arden St. Ives compare/contrast with Fifty Shades? idk I can do what I want) and will probably try to cover some different subgenres and time periods, but because I previously only read stuff I liked / happened to be recommended I know there's books out there I haven't even thought of.

Please help me out and suggest a few titles you think would be interesting to study + why you think they would be great on a college syllabus. What aspect of the romance genre do you think we could learn through studying them?

Thank you!