The Neighbor Wager is a contemporary romance. I bought my copy new.
Review:
When they were kids, River lived next door to Lexi, the beautiful girl of his dreams, and her sister Deanna. He never really felt like he fit in. Lexi and Deanna basically lived in a mansion, and the only reason River's grandmother could afford to live in the same area was because she'd bought her house ages ago. Meanwhile, his mother was an addict who'd basically left him with his grandmother. Still, that didn't stop him from fantasizing that, one day, Lexi would realize that the two of them were meant to be.
Years later, Deanna and Lexi are in business together, trying to find investors for their dating app, Meetcute. Lexi is in her longest lasting relationship ever, 6 months with a guy she met through the app. Although she's happy, she isn't ready for a commitment, so she's horrified when one of their potential investors wants to make her, her boyfriend, and their future wedding (he hasn't proposed, and she doesn't want him to) the face of the app and the things it can accomplish for users.
Still, Deanna figures they can work with it somehow. Until River turns up again, and Lexi, who'd previously never paid much attention to him, is suddenly intrigued by his attractive looks and tattoos. Knowing that the future of Meetcute depends upon it, Deanna becomes determined to keep Lexi and River from spending much time with each other. As sparks start to fly between Deanna and River, everyone finds themselves having to figure out how they really feel.
There's also a drunken bet, Lexi taking a brief "break" from her boyfriend, River worrying over his grandmother's health issues, and everyone talking about romance and sex at some point or another, but you get the idea.