These are the book, probably most of them found on my GR recommended reads, because I never heard of them before, and maybe neither have you
Shades of Gray by Brooke McKinley
First Published 19th of October 2009 by Dreamspinner Press
Contemporary mystery Romance
Miller Sutton, a by-the-book FBI agent, is starting to see some troubling shades of gray in his black-and-white world. He comes face-to-face with his doubts in the person of Danny Butler, a mid-level drug runner Miller hopes to use to catch a much larger fish: Roberto Hinestroza, a drug lord Miller has pursued for years. Danny has no interest in being a witness against his boss, both out of a sense of twisted loyalty and because he knows double-crossing Hinestroza is a sure death sentence. But he reluctantly agrees to cooperate, and as he suspects, it doesn't take long for Hinestroza to figure out the betrayal. Miller is surprised to discover Danny's not the career-criminal lowlife he expected; at the same time, Danny finds himself helplessly attracted to Miller's innate goodness. They barely begin to explore the sparking attraction between them when Hinestroza's hitman tracks them down, and then they're on the run, both for their lives and for any kind of love.