I don't really read romance books. And I could probably come up with a book that had a significant enough amount of romance that it would count, but that's boooring. Fuck tha police.
House of Leaves, by Mark Z. Danielewski
This had to be on here sooner or later. I'm not even gonna try to explain it because it's unexplainable (furthermore I've already tried here). I'm just gonna leave you with this quote from the author.
"I had one woman come up to me in a bookstore and say, 'You know, everyone told me it was a horror book, but when I finished it, I realized that it was a love story.' And she's absolutely right. In some ways, genre is a marketing tool." (source)