I must start by saying I have never really been much of a sci-fi/alien fan. I've enjoyed other books by this author, so I thought I would give this a shot. It took me quite a while to get into this story, as it just didn't grab me for some reason. Maybe I had a hard time believing the alien aspect of it, I'm not sure.
I liked Zach's character. He was sweet and had a good attitude given the way he grew up, with his father's involvment with the aliens, etc.
Of course, I immediately took to Raven - he was the injured party, couldn't speak and just seemed like such a lost soul.
Come to find out, all is definitely not as it seems. As Zach and Raven get to know each other better, they end up taking things beyond the initial phase of just using each other. I liked them together at this point. Then, the alien stuff became more clear. I had a very difficult time picturing Raven in his au natural alien mode being with Zach. When I pushed that aside, I was able to see their trust in each other growing, as well as their feelings.
There were times when this got a little confusing for a few quick seconds, after the pov changes when I had to think about who was now doing the talking, but I think it helped to see both sides.
There is a bigger picture, of course, with Raven leading the other aliens back to their planet. The action picks up in the second half of the book, and I ended up interested in getting to the end to see how things would turn out.