This is a science fiction novel with a very cool world. The story deals with some humans dealing with an ancient technology (including an expedition to find the makers and learn to turn it off). It reminds me of the Ringworld books, although the scale of the engineering is even bigger.
The characters were interesting too, with a contrast between a retired explorer, now family man, and up and coming explorer in shared command of the mission.
The story leaves a lot of the facts about the world implicit, only explaining those that the characters come to understand along the way. This feels quite natural.