Published in 1994, Mysterium is a shorter, less ridiculous version of Stephen King’s Under The Dome. Both stories are about what happens when an alien artifact ends up in a small northeastern town. In King’s version, the town of Chester’s Mill is trapped under an impenetrable alien force field. Chaos ensues as the town’s serial killer, meth cook, and rapists collide with a drifter who voted for Barack Obama. In Wilson’s story, an accident at a secret military base transports the town of Two Rivers to an alternate America where the government is under the sway of Gnostic Christian secret police. It’s a strong argument for plot economy that I found this premise significantly more realistic.
In addition to sharing several story beats with Under The Dome, the alternate America Wilson describes in Mysterium is remarkably similar to the post-apocalyptic United States he would later write about in Julian Comstock. French is a predominant influence on the evolution of American English, and pantheistic Christianity has suppressed public mores to Victorian levels. The conflict between the two Americas is sealed in a microcosm– the citizens from our timeline never leave Two Rivers– but sufficient background is provided about the alternate history for it to feel both present and threatening.
The slow-building tension surrounding the discovery and subjugation of Two Rivers frays as the book rushes into a ticking-clock scenario, but Mysterium is otherwise a tight science-fiction thriller with a logical and imaginative resolution. It may seem less unique now, more than 15 years after it was first available in print, but the collision of the higher sciences and mystery cults sets the book apart from its modern high concept successors.
 There are echoes of Mysterium in the later seasons of Lost as well.