Avion by Eve Langlais
Avion has been in the story line for the past two or three books now. Injured and near death, the cyborgs return to Earth to try and find the origin of their tech to see if they can jump-start his system with some new nanos. But they run into a lot of bumps along the way - including a strage woman who calls herself One.
One is a very intriguing character, and as I found out more about her, she grew on me even more. She has a strange dual personality that she's contantly wondering which is really her. She brings up tons of interesting dynamics that really throw the Cyborgs for a loop. If what she says is even partially true, then the Cyborg world will be changing drastically.
One and Avion make an odd pair at first, but they are connected in a way that seems to defy logic. Their's isn't a traditional romance, but they aren't very traditional characters either. From the very beginning they just seemed to fit together and it was so much fun watching them teach each other exciting new things.
While many of the earlier books in the series can be read as stand-alone romances, in order to truly enjoy this one, you will want to read the previous books. Otherwise there will be parts you just won't understand.
