Alive by Scott Sigler

You are twelve years old and the next thing you know you are gasping for breath and struggling to free yourself from a coffin. The school uniform is the only thing about you that looks twelve and you can't even remember your name let alone why you were locked in a coffin - and then you hear the others.
One young woman will lead but many will try. Some will even die trying but one thing is certain - they must survive and to survive, they must stay together. I think the scariest thing in a situation is the unknown. Once you identify the bad guy you can defeat him but in "Alive" you don't know what the monster is. This "jump out of your seat, stay up all night reading" thriller is for adults but young adults will truly enjoy the dystopian feel. It gets my scariest book of the summer award.