Loretta Chase, Lord of Scoundrels. My favorite romance-as-such book - good dialogue, great women, a dude who is hilariously fanfic-y in that he has Deep Feelings He Can't Express (if you read it, you'll see what I mean, or I can just tell you) - funny in that way where you kind of getting the feeling Loretta Chase is taking the piss out of the genre tropes.

I'd go with Freedom and Necessity by Emma Bull personally, but that only has one sex scene, so I don't know if your club would want it, and not that the romance is central at all (it's a historical novel about the Chartists and is AMAZING), but exploits some romance tropes. But if you need one that fits their bill more, I'd go with Lord of Scoundrels.