Ok so really I read the omnibus but since they are listed separately I'm going to review them separately too. Certainly in this case Wool 5 is a "book" not just an instalment anyway. 
 Howey's world building closes the circle somewhat in #5. We learn more about the past, we see the uprising cycle repeat itself and then yet right in the deepest moment of bleak despair there is a little offering of hope. 
 I could not put this one down. 
 This is an excellent post-apocalyptic/dystopian series.