First of all, the cover sucks!  It does not reflect the plot of the story (other than the fact that there are five main characters). It looks kinda cheap.
The book starts with a pretty violent cinematic escape: "Subject Seven" had broken out from his cell in the lab and he pretty much killed everyone along the way.  As the alpha of the group, he then tried to contact and "wake up" four other teens who were just like him: assassins asleep in the bodies of teenagers.  These four teenagers had been waking up in strange places, sometimes covered with blood, and had been trying to figure out what's going on when Subject Seven contacted them. Not only did Subject Seven have to evade and outwit his creators, he also had to figure out how to take over "the Other", which is basically the "normal" teenager whose body housed Subject Seven.
The beginning few chapters were quite confusing, and even when you realize what's going on and the fog clears up, you're still not quite sure where the writer is going with this. The suspense is definitely there, and the whole alter ego thing adds another layer and was more interesting than just the usual teens created by science experiments trying to get revenge storyline. I kept reading because I wanted to find out if the assassin alter egos are going to eventually win out or not, but since they are kinda unlikeable, it's hard to pick which side I  sympathize more with.  There is also no resolution to all of this, so I'm assuming there's going to be a sequel.  The book has its moments of brilliance, but not quite enough to wholeheartedly recommend it. It has some fairly violent scenes so probably more appropriate for older or less sensitive teens.