In a future Earth, there are a number of location where strange structures have appeared - presumably alien "cities". The appearance of the alien structures coincided with the explosion of any substantial piece of nuclear material (warheads of nuclear weapons, fuel of nuclear power plants). In some unknown way, anyone who approaches the alien structures with hostile intent are driven mad or at least disoriented. There are "no mans lands" around each alien structure. The aliens aren't seen coming out, but bits of alien devices or other artifacts are found in the vicinity. National governments have no control in these no mans lands, but some people live or work there. Religious cults that believing the structures are "cities of angels" live in those areas. "Free traders" who buy found alien artifacts and sell them elsewhere work the areas. There are also warlord-like leaders who try to rule such regions.
US officials learn that the warlord in the region around the alien structure in Russia has actually had a way to take artifacts out of the alien structure itself.
Meanwhile, in the central US, bit by bit government agents have been piecing together an alien device.
The feel of much of the book is post-apocalyptic - not one of my preferred sub-genres. To be fair, the explosion of nuclear materials and the effects of the alien structures have not left civilization as backwards as one often does in "post-apocalyptic" novels. The investigations into the alien structures give us a truly advanced aspect. (On the other hand, I didn't find the structures to be convincing tech, and there didn't seem to be a good reason why they should need to be on Earth.)