The story itself was pretty good, it paced well and I loved the thought that went into how an alien invasion would go down. 
 That said the romance was creepy and I'm tempted to knock it down a star just for that alone. (More about that below) 
 (view spoiler)[ I was so grossed out by the first kiss scene between Cassie and Evan. He kisses her. She tells him not to kiss her. So obviously he kisses her again. She then tells him to stop and then threatens him with violence if he does it again. He thinks that's just so precious that he kisses her AGAIN. And then he crawls into bed with her and tells her that she can't ever leave with out him. And. It's. Romanticized! Because nothing screams romance like not respecting consent and then telling a girl she can't escape you. It must be true love! (hide spoiler)]