It is like someone else noted, this is Catholic SF. If you are not into religion and are offended (lol) by Christianity then bypass this book, but if not then you are in for a really interesting ride. The book is essentially three books. Each book progresses the story by centuries. The world has been destroyed by nuclear weapons and what knowledge there is has been saved in pieces by a monastic order. Which in turn, when the time was right, brought the knowledge back into the world. Much of this can be seen having happened already in Europe during the dark ages, so the ideas presented in the story are not very farfetched at all. The crazy thing is that knowing how the world was destroyed the first time by the end of the third book they just do it again. A sad and very possible future for all of us ....