Undetected by Dee Henderson - 476 pages
What interested me the most in this book was Gina's discoveries. While all may not be possible yet, they are interesting to read and think about. For example, one is using reflections from solar flares to detect where submarines are in the ocean. For a security standpoint, I think all the science in this book is either older and declassified or is made up, but theoretically possible sometime in the future.