I think the thing that bothered me the most about the book, as many other reviewers have mentioned, is the instalove. It was almost Romeo and Juliet-esque. I mean, the entire book took place over about a week and by the last chapter they were declaring their unending love. I'm pretty lax on this usually, but in ORIGIN it was the Mary Sue of all instaloves. She'd never met a boy her own age before, she was the most beautiful girl he'd ever seen... Badabing badaboom.
I will add as a note to this review that some people have addressed the subject of animal cruelty. Yes, it is quite prevalent. From chapter one you are introduced to the kind of experiments that happen in Little Cam. They are shocking, they are disturbing, but on the whole I felt they were necessary to the plot. Khoury was not gratuitous with her cruelty.
Overall, I enjoyed this book and I believe that others will, too. I'm only giving it three and a half stars instead of four for the instalove. A lot of people must not mind that, though, since it's pretty prevalent in YA. I probably won't reread this book, but I do look forward to seeing what Khoury writes next.