Looking for a book on writing romance?

I don't want to write an actual romance novel per se, but I would like to be able to add romantic elements to my fiction. I'm looking for a how-to book that can help me get better at this.

Simply put (at the risk of repeating myself), I want a book that will help me learn to add romantic elements to my fiction.

I'm not opposed to the idea of a book that focuses on teaching how to write an entire romance novel, as I'm certain I would be able to extrapolate and only add elements of what I learnt (from said romance novel how-to book) to my (non-romance) novel that I would be writing... Clear? Hopefully?

I just want something that's good. Really good.