One clean science fiction romance novel is 'Cinder' by Marissa Meyer. It's a retelling of the Cinderella story set in a futuristic world where Cinder is a cyborg. There's a lot of cool science fiction stuff like a plague threatening the lunar colony and Cinder's own mechanical parts. And of course, there's a romantic subplot between her and Prince Kai.
Sure. 'The Host' by Stephenie Meyer is a great one. It combines science fiction elements like alien invasions with a love story. The main character, Wanderer, is an alien who inhabits a human body and falls in love with a human man, Ian. Another is 'These Broken Stars' by Amie Kaufman and Meagan Spooner. It's about a starship crash and the relationship that develops between the two survivors, Lilac and Tarver, in a hostile environment.