Star Splitter

What makes you you? In the world of Star Splitter, teleportation is accomplished through 3D printing of humans. You are "recorded". the old version is destroyed and a new version is printed. The "new version" as all your memories and is just as much you as the old version. Protocols ensure that only one version of you is around at a time. If something happens to you, they can always print a new version of you from the last saved copy. This allows for a degree of security for people that engage in dangerous exploration.

The book tells the story of a girl who reluctantly was teleported to a distant planet. She didn't really want to go, but her parents thought it would be important for her to spend time with them on their distant explorations. However, things don't turn out well. She wakes up in the "printer" with nobody around. She manages to get out, and eventually finds the only person there was a copy of herself who was printed a short time ago. There are not supposed to be two of them around, but they are also the only survivors. The "older" version of her tells a story (short on details) that everybody else had died and that the printer accidentally got kicked in to produce her. 

The story continues with two intertwined threads. The "old" one tells the memories of the first version as she came to and experienced life with her family and other crew members. The second is from the point of few of the "new" girl and describes her experiences (and interactions with the "old" one.) The "old" girl is hiding things from the new one. (And we know some of the things that are being hidden.) However, there are bits of the experience that "new girl" somehow knows without ever actually experiencing them. "New" lies a lot to old, but she has her reasons. 

There are battles and arguments between the two. Both are almost identical. The vast majority of thoughts and experiences are exactly the same. However, there are significant differences in the last few weeks. How does this change how we are? Can we really hope to hide some experiences from a version of ourselves? Would there be some "thread" that ties all different versions of this self together? If we ever have teleportation these would all be some of the various challenges to overcome. (And this doesn't even include the basic technology.)