The premise of this book sounds like a Dr. Who episode. It is kind of like present day people go back 200 years in the past, but instead of bringing modern science and technology to impress or deceive the populace, they have psy-powers.
This is always fun concept to dig into, despite not being very innovative. The twist, however, is that the world is one without wars or dangerous predators. Now the mental exercise is not about these "rejects," but how would the world have evolved? How would the technology develop? How would governments develop? How would philosophy and religion develop? The book isn't so deep to ask any, but the first of these questions, but it had the potential to be much more interesting.
Beyond that, the rest of the book is meh and okayish.