Death Sentence is the third book in the Furnace series. In this book, some creepy stuff happens, namely that Alex is transformed into a blacksuit. Alex, remembering what Monty said, manages to keep a lot of his humanity while following the warden's orders. As he, Zee, and Simon try to figure out a way to escape the Furnace, something is stirring, something scarier than they can imagine.
This book brings in the element of uncanny sadness and anger within Alex. These two elements combined make for an exciting story of betrayal and survival. Anyone who has read the series must read this book, and anyone who hasn't must read the series.