It first appeared promising, but then the narrator went into lengthy descriptions. He tells instead of shows for the most part. It's more explaining than exploring. I don't know if this continues after where I left off at 47%. 

I loved the idea of there being another group of people underground with customs and norms different from what we know on Earth. However, this was explored in a way that made me feel like I was studying for a test. 

Read if you like heavy description. None of it is purple prose. It's flat, in my opinion.