OOOOOH! this is my 2,000th review! think hard about balloons and cake and it will be like we are having a celebration! 
 this book is 215 pages. and that's 215 YA pages, with all the normative font/margins/pacing of YA. which means you can read this book in an hour or so. now for me, doing my "catch-up on YA series i started and never finished" program it's fine, cuz i have the third book right here ready to go. but how very frustrating for people who were reading this series as it was published, to be teased with such a shockingly short book and then have to wait a year for the resolution. sometimes procrastination pays off. 
 so yeah - it's short - it's real short, but it's still a tense and enjoyable book. in case you missed karen's review of book one, this series is about a group of kids ranging in age from 5-17 who are holed up in a superstore in monument, colorado after NORAD's chemical leak whoopsie causes blood type-specific symptoms in anyone who breathes the air. depending on your type, you could suffer blisters, sterility, paranoia, or if you are type o, turn into a berserking violent monster. so you'll want to stay indoors. 
 which is where they are in book one - caring for the littler kids, raiding the store for supplies and comforts, and surviving better than many. however, they still face threats because there are plenty of other people who would love to be in the safety of a superstore, and they're not all polite or in control of their impulses right now. 
 in this book, the survivors break into two groups - most of the kids pile onto the school bus in their masks to try to make it to denver airport, where the refugees are gathering for evacuation. the plan is to get the kids to safety and then send help back for those left behind; the (mostly) type o's, who stay in the store to keep the non o's safe, just in case. the story is split between dean, who has stayed behind, and his younger brother alex, on the bus. 
 this is a smart development, so the reader doesn't feel bored or claustrophobic being stuck in a store for the whole book. and yet, again, there is just as much action in the store as there is in the greater, much changed world. i love all the store stuff. i love how dean isn't a traditional hero, just a kid smart and practical enough to take what he's given and repurpose it into making the store more homelike for the scared little kids and using his innate cleverness to survive the threats more dangerous than their homesickness and whining. 
 i like all the moments where their own inexperience causes unforeseen difficulties - why yes, how will we feed these kids outside if they can't take their masks off?, or when they struggle to figure out the correct dosages of medicine for little kids (view spoiler)[or a dog (hide spoiler)] - i like how those details add a layer of realism to a premise that otherwise is toeing the line of absurdity. i liked the josie twist, i didn't understand the mr. scietto thing (view spoiler)[so he's got his wife's dead body in the bunker - it's not like he killed her, jeez. (hide spoiler)], i'm glad that (view spoiler)[ only some of the kids were reunited with their parents by the end because again - realistic (hide spoiler)] and overall i think it did what a middle book is meant to do - progress the story into new territory, clear up some questions, and set the scene for the big finale. 
 i am very grateful for that four-page exposition-rich prologue, and even though this series is dopey at times, it's a lot of fun and i look forward to seeing how it concludes. and i don't even have to wait a year to do so! suckers! 
 oh, and i JUST LEARNED - there are no fewer than THREE free tor shorts connected to this series. which i will also read soon. score! 
 http://www.tor.com/2012/05/16/dress-y... 
 http://www.tor.com/2013/06/26/jake-an... 
 http://www.tor.com/2014/04/15/what-ma...