The more I think about this book, the more I like it because it's a deconstruction of religion in a way that isn't anti-religion.
Disclaimer, I grew up Mormon. This book hits a lot, a LOT, of things that trigger my Mormon Doctrine sensors. Similar to books by Card or Sanderson. I would not be surprised to learn that Hawkins had an LDS background as well, I mean, he may not, but I really wouldn't be surprised if he did.
I'm not sure how much explanation I can reasonably do without disclosing to many spoilers. But I just love so much about the book and the revelations in the last few chapters.
I've seen a couple of requests for a sequel. I just don't see that being possible. At least not in a way that is true to the themes of this novel.