The Roommate and The Marine (Dark Fire #4)
Ivy M. Jones

Dating is a disaster, until one night when a guy at a bar opens with a line she's never heard before… "My friends and I have a bet. I have fifteen minutes to get from asking if I can buy you a drink to getting you in bed. How far is your place from here?"
It's not even slightly romantic, but Lucy is at the end of her rope and some hot sex with someone who isn't trying to use her for her connection to Dark Fire sounds like the perfect night. And it is.
It might have been the perfect one-night-stand, but that's never the end of the story, now is it?
-Book Four of the Dark Fire Series-