There are numerous mysteries in this story, many of which are
explained as the narrative progresses, but there's one central
enigma which is never addressed. I haven't read the prequel
nor the sequel, and perhaps they deal with it, but this book was
written first as a stand-alone, and read as one, it leaves
this reader puzzled.
The silo has abundant energy produced from oil wells drilled
from the lower levels, sufficient to provide artificial lighting
throughout including enough to grow crops on the farm levels.
There is heavy machinery: pumps, generators, air circulation and
purification systems, advanced computer technology in IT, and
the infrastructure to maintain all of this along with a
logistics, maintenance, and spares operation to keep it all
running. And, despite all of this,
there's no
elevator! The only way to move people and goods among the
levels is to manually carry them up and down the circular
staircase. Now, I can understand how important this is to the
plot of the novel, but it would really help if the reader were
given a clue why this is and how it came to be. My guess is
that it was part of the design of the society: to impose a
stratification and reinforce its structure like the rule of a
monastic community (indeed, we later discover the silo is
regulated according to a book of Order). I get it—if
there's an elevator, much of the plot goes away, but it would be
nice to have a clue why there isn't one, when it would be the
first thing anybody with the technology to build something like
the silo would design into what amounts to a 144 storey
building.