What if the quickest way to travel was to transmit your thought-state to another world so that you could be "uploaded" into a new body? What if you were "broadcast" and folks in several places uploaded several copies of you into several bodies? Then you might end up with a book with a split protagonist.
That's this book's premise; two copies of one personality go through different experiences and thus make different choices. Maybe if I were better at figuring out the reasoning behind those different choices, this gimmick would have seemed amazing to me. As it was, it seemed like a sci-fi action novel awkwardly smooshed together with a twin study.