That's a LOT of worried end-timers
"Biblical Literalism" they call it. I call it fear tactics. Remember the old 70s movie where folks got raptured, and left behind and by the end kids were still wetting their pants in fear as they ran down the aisle for "salvation"? Same thing.
AND they're getting rich doing it. Even if it's a buck a book, which it's not....
When I was working part time at Barnes and Noble we joked that the books were called "Left Behind" because slow readers couldn't keep up with how often they were released one after the other.
Some of these readers must just be sci-fi fans, but I daresay most are Christians who are scared that the books calling themselves "Biblical Literalist" must depict how it will really go down. And so they spend, and spend again. Fear Tactics.
ASIDE: even if it is a LITERAL interpretation of the book of Revelation, let's remember that the first lines of the book itself let us know that it was all a dream, yes?