Shift suffers from prequel syndrome.

While there are more mysteries and reveals, there isn't as much mystery as in Wool.

I prefer stories where people are struggling to overcome a bad situation, and wool is certainly such a story.
But I sometimes have a hard time with disaster stories where you know your the people are heading for certain disaster and you just watching them walking into the trap.

Each of the Shift stories contains part prequel and part new reveal. The first shift had the most prequel and I had a hard time finishing it. The second shift was still a bit of a slog, but the third shift like like the Wool stories I just couldn't put down.

Looking back from the end of Shift Omnibus, I can recognize the importance of the character and relationship building that took so long in first shift story. But while I was reading it I was having a hard time.

The most impressive thing about Shift is the feeling of claustrophobia it instills in the reader.
It is not a physical claustrophobia induced by the setting, but a psychological claustrophobia induced by the Orwellian setting the characters find themselves in.
We are not sure what the truth is and there is a sense of impending doom and I'm still not sure weather keeping or breaking the rules is what will save or doom humanity.