Like Wool, the second volume in the Silo series started as a set of linked novelettes. The narrative begins hundreds of years before the events in Wool, with Donald, a newly elected US Representative, being brought onto the Silo project. This is before the apocalyptic events leading to the occupation of the silos, and gives background on how it all came to be. Donald is an unwilling accomplice in the control of the subsidiary silos as he slowly realizes how he, and the entire complex, has been manipulated, with conspiracy nested inside conspiracy aimed at a mysterious goal. Another section deals with how Solo from Wool came to be alone in his dying silo for decades.
While Wool was, despite its dark setting, a story of hope and searching for a better future, Shift contains very few bright points. The parts about Solo and his solitary descent into quasi-madness are especially bleak. Donald struggles with his conscience, his desire for revenge, his realization that even knowing the truth is not going to make things better. While the mental battles were well written, I felt that this book could have been trimmed to make it a bit less of a slog at times.