"It's hard to write something new about the end of the world," writes Crawford Gribben in Books & Culture:
What is interesting about much of the comment on the Left Behind phenomenon is the assumption that this market did not exist before the publication of the series' first novel. … The opposite is the case. Rapture fictions have been a feature of Western evangelicalism throughout the 20th century, and end-times novelists have repeatedly rewritten the apocalypse to take account of changing social and political concerns.
Gribben traces the genre back to the British writer Sydney Watson, whose end-times trilogy — Scarlet and Purple (1913), The Mark of the Beast (1915) and In the Twinkling of an Eye (1916) — established the basic template on which later writers, like LaHaye and Jenkins, based their works. Gribben does concede that these later novels are bound to be similar to Watson's in that they are constrained by the same laundry list of "prophetic" events that must occur in lieu of an actual plot:
… when both authors and audience share a basic commitment to dispensational theology, it becomes extremely difficult to develop new contours in plot. A narrative paradigm has been established by biblical exegesis, and no author who takes his market seriously would dare to challenge its fundamental conventions.
The Left Behind series, covering the same imagined sequence of events that Watson covered, is bound to have some similarities, yet Gribben notes that it's more than that — L&J borrow several tropes and stock characters as well:
Watson's In the Twinkling of an Eye features as its protagonist a 30-year-old bachelor journalist named Tom Hammond. His career in crisis, Hammond is offered the opportunity to launch his own paper, which quickly establishes itself as the most successful in the world. Hammond editorializes in a column called "From the Prophet's Chair," in which his growing interest in biblical prophecy develops. Buck Williams, in the Left Behind series, is also a 30-year-old bachelor journalist who launches his own internationally successful news portal and uses it to display his growing interest in biblical prophecy. Perhaps there is something to be said for narrative economy. …
At best the novels are deeply intertextual; at worst, it might even be claimed, elements of their fictions are explicitly derivative.