The Adversary Cycle
The Adversary Cycle is a series of seven novels written by American author F. Paul Wilson. While it was originally known as "The Nightworld Cycle" (this name is even printed in the front of some early editions of "Nightworld"), John Clute, in his section on F. Paul Wilson's work in "The Encyclopedia of Science Fiction", kept referring to "the Adversary." The author liked that better and so renamed the cycle. Novels. The seven novels that comprise The Adversary Cycle are (in chronological order): However, the book series does not fall into a strict chronological order, with  alternative orderings suggested. For example, Wilson's website suggests an order of "The Keep", "Reborn", "The Touch", "The Tomb", "Reprisal", "Signalz", and "Nightworld". "The Tomb" and "The Touch" were initially written as stand-alone novels; it is only in "Nightworld" that they were retroactively made part of the Cycle as their respective protagonists all come together to fight the final battle against the Otherness. Although these seven books make up the "core" of "The Adversary Cycle", many more novels and short stories tie into the series. For example, "The Tomb" is also the start of the Repairman Jack series of  novels, which quickly became deeply entwined with the Adversary Cycle. They take place in the last three years before "Nightworld" and include some of the main characters from the original Adversary Cycle. This is all part of the "Grand Unification" theme of Wilson's works known as The Secret History of the World.