first things first. look how cool this book is when you take the dust jacket off: 
 and i appreciate that attention to detail, but when all is said and done, this is just another book that has a great premise, but suffers under any real common sense scrutiny applied to its plot. 
 this is a puppy-dumb YA book that reminds me that these books aren't written for me. i think younger readers will appreciate a book about people being quarantined in a mall after an attack by unknown enemies where a bomb starts pumping deadly disease in through the vents and the confusion and death that ensue. teens, trapped in a mall with other teens and prospective love-interests = fun!! me, trapped in a mall with roving gangs of teens with their friends and prospective love interests = no way, get me out of here. 
 and i can't help but point out the flaws in the crowd-control elements, and the unrealistic passivity of the detainees, for the most part, and especially the employees who are just at their registers for hours and hours, waiting patiently for a quarantined individual to come in and buy a pair of pants. why are these people still working at the stores? just hanging out, manning the registers waiting for someone to maybe wander in and buy a book? i work retail and i can tell you that these systems would have broken down much earlier than this. when there is a rainstorm, people go helpless. i have heard all manner of uncivilized behavior explained away by "but it's raining out." can you imagine these people being locked up in a mall for a week without access to showers and proper food and clean bathrooms (because the cleaning crew only works at night? seriously? so in this mall, not a single janitor is on hand during the day in case a pipe leaks or a kid throws up on the merry-go-round. really??) they would not still be buying their clothes, let me tell you.there would be way more looting and resentment and probably more violent crimes and i guarantee you no one would still be running the stores. i would, because i am an incredibly devoted worker bee, but most people would not still be there, biding their time, punching in their timecards. 
 and eventually, people do begin reacting in ways that are less-civilized, but seriously - too little, too late, too unrealistic. i am telling you - people are animals. 
 and then to find out that this is just the first book in a continuing series? nooo. at 263 pages, this hasn't really earned itself being a part of something. write more of this book and then you may write another one. 
 i'm being overly harsh here - it's not bad. it is a fun idea, and the big reveal towards the end (which also makes no sense, realistically, but whatever) is shocking (mostly because it makes no sense, realistically) but maybe the next book will be stronger. 
 it's fun, really. just dumb-fun.