I love time travel paradoxes in science fiction, and this is a terrific, and very exciting example. Em and her friend Finn are sent back in time from our near future in which America has become a police state at war with itself, to kill the inventor of time travel before he invents it. Unfortunately for Em, the inventor is James, the love of her (past) life. The person helping James to stop this from happening, is her past self. This sets up a great scenario for drama, action, paradoxes, romance, betrayal and conspiracy. A great read for teens, with elements of Terminator, Doctor Who and The Hunger Games.