A serious disease has wiped out a sizeable chunk of the human population, but it has a weird side effect--some people who contract it come back after they die. They are called Reboots, and the longer they were dead before Rebooting, the less human they seem to be. Reboots are stronger, faster, and heal quickly, so the new government uses them as a sort of Special Forces. But they're also experimenting on them, and things are starting to go wrong. 
 Writing from the POV of a character who isn't quite human is generally a difficult endeavor. After all, the writer is human and has fairly generically human thought patterns; thinking outside those parameters can be difficult (witness the many many vampires who are several hundred years old yet act like teens or twenty-year-olds). Tintera actually did well in this regard, partly because Wren 178's emotional patterns are actually quite human--she's been through some trauma and she's been told that she's less human than she is, so she expects to be cold and emotionless, but in the right circumstances, she discovers that she's not. Likewise, her early emotionlessness is described well; she recognizes certain emotions in others and knows how to act like she feels things to make other people happy or comfortable, but until she allows herself to emotionally connect to another Reboot, she doesn't quite understand those feelings. And until she accepts that her lack of emotion is part of the indoctrination she gets as a Reboot, she doesn't understand her own emotional reactions to things. 
 My only complaint is that the biology is a bit internally inconsistent, but the inconsistencies had no impact on the plot, so I could suspend disbelief in that regard. 
 Reboot should appeal to fans of Veronica Rossi's Under the Never Sky series.