“After having a routine exam that turns out to be anything but routine, Robert learns about the mechanical parts and plastic casings that make up his being, forcing him to flee the only world he has ever known and go on a dangerous search to find out who (and what) he is.”
Robin’s Note: Kevin Brooks has a lot of fun skating along the edge of what’s possible in this book.  What would happen if you woke up and weren’t quite human anymore?  He doesn’t concentrate on the science but instead on the confusion – how can you find out what you are now, and why would anyone do this?  The chase starts almost immediately, and doesn’t let up.