Possibly 4.5 :) 
 Wow. This was different. An original plot, well at least one that I've never read about. It was interesting and completely caught me off guard. 
 Especially the romance, at the beginning it was one of those instant attractions and I was like "Oh no, please no! Don't be another one of those books!" and when there was an almost lip-lock the second time they met I was even more worried (even though the instant attraction thingo was actually well written, because it was.... but I was in the mood for a developing one not a quick kiss-then-together-forever kind of one). 
 But yea, even though the instant attraction thingo had a reason to it it was sort of developed through the book (at a good pace I might add (from then on)). So much so that by the end of the book I was completely horrified at the ending. I literally stared at the wall, I happened to be siting opposite at the time, for at least 30 seconds going "Wait, what? What? She ends the book like this? (view spoiler)[ no kiss!!!??!! And after all that chemistry?!?! Boy, there better be one heck of a kiss in the second book! :P haha (hide spoiler)] 
 If you don't read the spoiler I guessed the ending, there was jut something that wasn't present in the ending that I would have appreciated :P 
 Anyways, a lovely read and I will definitely be reading the sequel :)