The world-building is on the slim side: little to no page-time was given to detailing technologies, weaponry or even alien hierarchy. I found this to be good, as it didn't get in the way of story progression. In fact, I finished the book in two days, proof that it was quite a page-turner.
Religion and spirituality plays a big part in the story, though it was never pushy or preachy about it.
All in all, I highly recommend this book: if you like sci-fi or military fiction, this is perfect casual reading for you.