I originally picked this up because the tag-line looked like this book would be about Roko's basilisk. While this is technically not wrong, the concept really just plays a world building role (like FTL travel and ansible communication) rather being the focal point of the story. It is not even explained, just implied and the reader is expected to know about it already.
The main theme of the story are cosmic horrors and the relationship between science and spiritualism, done in a very interesting way. It should be noted that although this is about cosmic horrors, it is not at all scary. Overall, it was not at all what I was expecting but nonetheless very nice!