Interesting book that reminded me of Helicopter Man in Part One as the premise is very similar at the beginning, Billy lives with his mother Sylvia after his parents were divorced. His mother is obsessed with teaching Billy survival skills and makes him memorize everything from a "How to Survive" pocketbook that she treats like a bible. Lately though, she has started acting stranger and more paranoid - taking Billy out of school early, quitting her job, believing people are following them and going out late at night with boxes of goods. It all comes to a head when she starts a fire in their apartment trying to burn some incriminating paper and she has to push Billy out a window to save his life.
Sylvia is then sent to a psych ward and Billy is sent to stay with his father Steve, who he hasn't seen for a few years. Billy is convinced that Steve doesn't want him, especially when Steve introduces Billy to his girlfriend and daughter and Billy is rude to the daughter. But meanwhile, strange things are happening....people seem to be turning grey and developing into shimmering monsters or , if they don't, dying and nobody believes Billy when he tells people what he sees (A survival rule is "BE OBSERVANT") except his new friend Anwar and Steve's girlfriend's daughter Angharad. (Think : Walking dead/Zombie Apocalypse)

What follows then is a race for survival across England with Billy using various methods that Sylvia taught him to try and reach the bunker ( tower) where she has escaped the psych ward and has headed to - -this bits a bit rushed and the ending where they learn how to defeat the Greys (zombies) came about very quickly but it is a kid's book about saving the world in a week so I shouldn't be too picky, should I? ( )