First, let’s clarify the search term. is not a standalone novel or a secret book by Hugh Howey. Instead, it most likely refers to a specific volume or compilation within the Silo universe.
Tell me which detail you're interested in and I can find the specific title or author for you.
Join the r/SiloSeries subreddit. If you cannot find the "233" reference, ask the community. They have encyclopedic knowledge of Howey’s world.