If the covers don't reveal romances (and that includes having vines and flowers sprouting from the cover's bottom), there are plenty of keywords found in titles that generally indicate a romance, like what's below in the spoiler (because so many just flowed out of my head and I don't want to clutter the thread with a long list):
My annoyance with romances ... When I first got my Sony PRS-505, Harlequin romance books were coming up free, so I gobbled them up for the women who might use my e-reader. I read several, and my annoyance with them is that the heroine generally has some creative job requiring no particular training, like decorator, and is fantastically successful at it without much lifting a finger during the story. She had plenty of time to spend at the ranch/castle and be irritated by the rogue with curly black hair and piercing green eyes. Are there any other storylines and any other character types in romances (excluding werewolf romances)?