I'm still half-way through this enormous book (about 1100 pages..) in which for the first third or so not a lot happens... and yet I was entranced by the time I got to the second chapter. At the point where I am a lot does indeed happen... I've slept very little on the last couple of nights, immersed in that world compelling and believable.
The book takes place in a world that is 'similar to Earth, but not Earth'. Up to this point, although there are science-fiction elements, it is not science-fiction as I would see it. The author seems to prefer the term 'speculative fiction'. In that world, there have developed sort of lay monastic orders whose job it is to preserve knowledge and advance it. The protagonist is a young man who belongs to one of this orders and is about to take his vows as an adult member of it. Then his world and the world at large come under a threat that can obliterate them. Told like that it might not sound very original or enticing but, as always, the devil is in the detail and, in this book, the detail is fantastic.
I'm still living in that world (have had dreams set in that world... that never happens) and have half of the book to go. Enjoying it enormously, thus far. I also suspect that this might not be to everybody's taste, with the slow start, the jargon and other peculiarities but it certainly is for me.