It starts with some dry facts abut the history of the protagonist's world and it continues bringing up, without explanation, facts and events about which we have no previous knowledge. These mysteries are resolved as the story continues. I suspect the author chose this method of introducing readers to a new cosmos, because if he had laid it all out schematically at the start, it would be quite boring. His is, after all, a pretty ambitious and wide ranging vision. After a few chapters I was beginning to have a basic idea of Stephenson's worldscape, but it was actually quite satisfying even toward the end of the book, when some features of the place that had remained mysterious throughout the story were elucidated in the context of the plot.
I started through the book a second time and found that the chapters that were boring at the first view, became more interesting now that I understood this neighboring cosmos a bit more. Like many good science fiction writers Stephenson does not neglect the human side of his speculative milieu. The values his characters struggle to define and preserve are a big part of what makes the book compelling.