Republic Under Siege: Threat from Within is a sci-fi thriller written by Michael J. Brooks. The book is basically the second part of The Wars of the New Humanity Series.
The first part, which features a book called Republic Falling: Advent of a New Dawn, tells the story of humanity being partitioned between two worlds (Eden and Satellite One) and the violent war that ensued. On the other hand, this book features life after that war and has a different tone.
