I liked seeing the different writing styles between the two MC povs. 

I understand why we don't get a definitive answer as to what the demon actually is, or what happened to the rest of humanity. But I still wanted to know!

The scene with the parallel speech was really cool.

The only other Tchaikovsky book I've read so far is Cage of Souls, and this honestly feels like a redux of some of the elements that didn't get a chance to play out much in that book. It definitely feels related, these two books are sisters.

For example, people banding together to solve a problem (overthrowing the government), and the development of what I'll call the Morphogenetic field (courtesy of the excellent Zero Escape series). These elements couldn't be explored in Cage of Souls as much due to the fact that most everyone disappears.

While I think I still liked Cage of Souls better, this was a shorter and more focused book, which I'm grateful for. Interesting ideas, as always.