This book is just plain ridiculous. Having sex while piloting a spacecraft and shooting aliens in a life-or-death situation? The fact that having sex while you're doing these things is supposed to make you a better pilot/gunner? And don't forget the 'I'm only raping you so we can save the world!' which is made even more ridiculous by the fact that the character being raped actually improves his marksmanship while he's being violated.
Reading the synopsis, I thought I'd stumbled upon an interesting sci-fi concept (and to the author's credit, I still think it's an interesting idea; I just don't think it was done well or believably in this particular story), but the whole thing reads like an excuse for the characters to get it on. None of the actual science made any sense to me and all the explanations and conflicts (not to mention the cookie-cutter antagonists) just felt like they were thrown in for the sole purpose of getting the main character to break down and finally submit. The romance never felt believable so when he does finally have consensual sex, it felt more like he had been manipulated into it, and I don't believe the happy ending either.