With the Earth in a state of ruin, mankind has retreated to living underground where a dystopian society has evolved to ensure continued existence. The inhabitants of the underground silo know that their self contained ecosystem is a fragile balance so they must dole out harsh consequences to anyone who disobeys the rules. These people have lived underground for generations and know nothing of how they got there or why the outside world is so inhospitable; however, they do know that crimes are punished by being sent outside through the single airlock at the top of the silo. The world outside is so toxic that even their best protective suits offer only offer a couple of minutes of life, yet everyone sentenced to die this way is asked to perform a vital service for the rest of the silo before they perish - a cleaning of the external sensors. Would you do such a favor for those who sentenced you to die?

Being sent out of the airlock is known as a "Cleaning" and it has become a weird combination of mourning and celebration for the silo. Leading up to a Cleaning the entire silo is abuzz with discussions about whether or not the person will actually clean the sensors. Amazingly, as far back as everyone can remember, all individuals so punished have indeed cleaned the sensors before walking off and dying. These deaths are witnessed by everyone watching through view screens that provide a much improved image due to the newly cleaned sensors. Why does everyone clean? Even those who swear ahead of time that their sentence is unjust and vow not to clean do indeed wind up cleaning when they get outside. Why is that? 

This mystery, and many others, are what makes this tale of the apocalypse so intriguing and Hugh Howey does a masterful job of slowly peeling back the onion and revealing this bizarre society in which the main characters live. The various rules of the silo, along with the mechanisms that make the society work, are slowly revealed along the way and each step adds another piece to an oddly compelling puzzle. Originally self-published on Amazon as a 5 part serial publication this omnibus edition is all 5 stories together in a single novel and certainly worth reading. If you enjoy this book then you can continue on with the rest of the series and find out how the world became the way it is and why the rules are the way they are.

For audiobook fans the narration is done by Amanda Sayle and she does a decent job bringing this unique story to life. Be warned that some of her voices can be annoying, surprisingly they are female character voices, but they are lesser characters so I was able to get past that and enjoy her reading overall. This book left me very intrigued and eager to move onto the second book, Shift.