Rob not to be smart but there is no "secular" take on a purely religious fiction such as the rapture.
Alana The Christ Clone trilogy actually was actually a better written series, in my opinion. Tells the story more from the perspective of a non-believer, viewing the Christian group as more of a fringe, right up until the very end. The characters are a little more believable. I enjoyed Left Behind to a point, but it does get VERY preachy. Christ Clone is a better alternative, if the preachiness is distracting.
Silvanus Slaughter See the 1992 Michael Tolkin film, THE RAPTURE with David Duchovny and Mimi Rogers. It's wonderfully out there and in there, as psychologically astute as anything tried in the 90s. Works on several levels, and is actually designed like an awfully done typical "Christian" proselytizing film--until it takes some wild turns. The issues of finding what is embedded deep in one's mind, and a willingness to forgive what one has conceptualized, are at the center. Mimi Rogers deserved an award for intensity. She is wholly obsessive and prone to projection. Most so-called Christians hated the film, because it had real content and asked one to think hard and deep about the 'rapture' itself. Nevermind it was all pretty much cooked up by Darby in 1820, and had few Christian scholars who would give it the time of day.