Going into this, I knew this novella was meant to hook the reader into the Wool series. The writing is fine, well edited and clear, but doesn't have the richness or depth to earn 4 or even 3 stars.
Two main characters are introduced, Sheriff Holston and his wife. Oftentimes characters are what draws a reader into a series. Time and effort are invested by writer and readers, and, hopefully, attachments are formed enough to carry the story forward. In this case, I haven't that sense of attachment or wanting to move forward, mainly because at the end, the main characters are both dead - which can work for a standalone short story, but not a novel series. Again, 3 stars for character development - they were nice enough.
So, how about the world building? Generations of people exist in an underground silo. While underground worlds aren't new, they aren't plentiful either, so I was intrigued. World building is challenging, and not as easy as one might think. [a:China Miéville|33918|China Miéville|http://d202m5krfqbpi5.cloudfront.net/authors/1243988363p2/33918.jpg] is great at it. [a:George R.R. Martin|346732|George R.R. Martin|http://d202m5krfqbpi5.cloudfront.net/authors/1351944410p2/346732.jpg] and [a:Cormac McCarthy|4178|Cormac McCarthy|http://d202m5krfqbpi5.cloudfront.net/authors/1302752071p2/4178.jpg] both come to mind. The underground world in Wool is less richly drawn. Perhaps the novella format is the limiting factor, but the right vocabulary can pack powerful punches in short order. So, for the world ambiance, Wool was okay -- 2.5 stars.
The theme has potential -- ideas about society, government, beliefs. I know the wool is being pulled over the population's eyes, but by whom and for what reason are leads for a good story. When it comes down to it, I found myself simply unmotivated to pursue them. Why? Something was missing. I should be one or more of these: 1) emotionally entangled 2) intellectually curious, or 3) in love with the prose. Because I'm none of the above, I have to rate this 2 stars, which is not a dig, but it was okay, without an exclamation mark.