This was an interesting read that raised some complex questions regarding identity, but there were quite a few frustrating aspects to it as well. Things like "we're going to continue keeping secrets even though that is obviously not
the best course of action and has led to the majority of the problems we've encountered to this point" and some scientific aspects as well. Specifically, cloning and how it would work. Even identical twins--the closest thing we have to human clones--are not 100% the same as each other, so why should Bethany be so similar to Elizabeth, down to favourite foods and hobbies and physical abilities and all the rest? It just doesn't seem feasible to me, even if we are looking at a science fiction story.
Still, all told it is a fun, fast-paced read, and for the intended audience it should be pretty engaging.