These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Angst? What Angst?: You'd think that the complete eradication of all kids under the age of ten would be a bit depressing, but people seem to take it in stride. Given how much disruption this would have on the global population, this approaches Cosy Catastrophe levels.
Not to mention, the often questionable interpretations of the Bible. For instance, the fourth horseman from the book of Revelation, also known as Death, is said to apparently be the Antichrist by Bruce Barnes, the priest. Thing is, the word "Antichrist" isn't mentioned a single time in the book of Revelation. In fact, opinions vary a lot on whether the Antichrist is supposed to be the name of a specific person or just an adjective, like "anti-communist." So having Bruce say that the fourth horseman is apparently the Antichrist is just stupid.
The plotline about the recruitment of Rayford, a civilian airline employee, as pilot for Air Force One. In case the name of the plane didn't make this clear, The Other Wiki has a list of all previous Air Force One pilots. All were military officers, none below Lieutenant Colonel.
How the fact that 'Air Force One' is an Air Force plane, not a civilian one, slips by you is anyone's guess. Why is this important for the authors to know? For one thing, Rayford is a candidate to be hired as the pilot of Air Force One despite being a commercial airline pilot rather than a military pilot. If this came about as a result of Nicolae changing the rules after taking over the world then it might have made sense, but one of Rayford's colleagues at the airline tells Rayford that he has been applying for the same position every time a new president was elected, despite being a civilian and long before Carpathia came along. Also, the President of the United States complains that Nicolae "...weasel[ed] me out of Air Force One...", seeming to forget that he voluntarily gave up this Air Force plane when he agreed to destroy 90% of his military arsenal and donate the remaining 10% to Nicolae's new Global Community.
On top of that, Air Force One isn't really a single, specific plane. It's a shorthand for "Air Force plane that the President is currently using or about to use". Strictly speaking, there can no longer be an Air Force One, since the term only makes sense in a strictly American Air Force context.
To say nothing of the fact that thanks to massive Values Dissonance, God and Satan Are Both Jerks, and like their minions have nearly the exact same goals: Nicholae wants to kill everyone who dosen't worship him, as does Jesus. Nicholae wants to take over the world and establish a one-world religion comprised of people who worship him, Jesus also wants this (and gets this in the 13th book in the series "Kingdom Come"). The only difference between the two is power-levels, and it is a massive difference. Jesus is so powerful that he comes off as a God-Mode Sue, while Nicholae is an Ineffectual Sympathetic Villain. The only possible motivation for becoming Born-Again is being on the winning side, not out of being moral.
Designated Hero: Buck and Rayford. Most of their behaviour goes beyond even the standards of a Sociopathic Hero. One could argue they're supposed to be newly-converted Antiheroes, but this doesn't hold up since they never do anything for anybody.
T. Mark Delanty from books 5/6/7 is also notable for two reasons. One, he called Rayford out on being a total jerkass and got the man to admit he was wrong (this is a Canon Sue he called out, by the way). Two, he's one of the few people in the books who actually comes off as genuinely good.
Jonathan Stonagal, a supporting antagonist who doesn't survive the first book, is surprisingly widely regarded as having had a great deal of wasted potential. It doesn't hurt that in the film adaptation, his character is actually played up something fierce, to the point that he comes off as a serious contender for the "Antichrist" position.
Loretta, the only person at the church seen to get things done while Bruce the pastor builds a hole in the ground to hide in with only his "inner circle."
Fan Nickname/Running Gag: "Fan" is a misnomer, but readers of the aforementioned blog by Fred Clark have made a running joke on Slacktivist of referring to Carpathia as "Nicky (insert mountain/mountain range name here)"; recently, a new nickname, Chairface Carpathia, seems to have caught on. Buck, the Greatest Investigative Reporter of All Time, is called the GIRAT. The authors (LaHaye and Jenkins) are often abbreviated to "Ellenjay".
"Meta-(character)" is frequently used by the same community used to describe any character who seems to be showing signs of behaving like an actual human being in the actual situation they are currently in. This title often confers a sort of temporary Ensemble Dark Horse status as well.
Misaimed Fandom: Among non-fans, it's hard not to feel more sympathetic for non-Christian characters (Chloe before her conversion, back when she was tough, independent and questioning), and to dislike the heroes, who come off as rather arrogant.
Moral Event Horizon: Nicolae crosses this when he was still a child by conspiring with Viv Ivins to kill his mother.
Narm: Quite a bit of it, but Carpathia's speech to the U.N. stands out, considering it's essentially a 4th grader's class report on what the U.N. is, followed by an alphabetical list of the nations that are members. One possible interpretation is that this is an Intended Audience Reaction, to emphasize his supernatural ability to win people over. He could read the entire contents of a telephone book to the assembled people of the U.N. and they would still be falling on their faces for him. Problem is, if that's the case then it still fails since you get the impression that the authors intended the speech to be good.
People are raptured without their clothes - thus, the raptured leave behind piles of empty clothing. So the first sign of the end of the world was a field of underpants.
In the Book of Revelation, the Two Witnesses are said to destroy any who threaten them with fire from their mouths. When they show up in this series, people who threaten them... collapse dead from heart attacks. The antifans have taken to calling them "the Trip-and-Fall Guys".
Newer Than They Think: The doctrine of the Rapture as presented in the series really only came into being 2 centuries ago at most.
Nightmare Fuel: The description of the final fate of Carpathia and Fortunato after 1,000 years in the Lake of Fire (writhing in torment in fire and brimstone and continuously crying "Jesus is Lord" over and over) with the understanding that they will spend eternity like that, not to mention all the unbelievers who are doomed to join them.
When Steele had a handshake with Carpathia. You don't want to see the latter's face.
Periphery Demographic: Many — if not most — of the books' readers were just mainstream agnostic Americans looking for a good supernatural thriller, like The Stand or The Langoliers (The first book has a very similar setup to the Langoliers; where people on an airplane awakening to find many passengers missing).
This is a problem with the series of books, as noted in the Slacktivist blog deconstructing it. The main heroes are such Jerk Sues that many of the people with whom they argue come off looking much better by comparison. For example, in the first chapter, a drunk Texan wakes up and sees the carnage wrought by the Rapture (plane crashes, etc). He is mocked as a silly drunk by the narrators, but he is the only one to express any sort of horror at the proceedings. In the next book, we are clearly supposed to cheer for the alleged hero as he is insubordinate to his boss — whose main crime seems to be being a woman who does not fawn over him and expects him to do his job.
Verna is constantly presented as a no-fun, uppity woman who thinks Buck is a pompous Jerkass. And she's right.
The "heroes" are supposed to be callous to the suffering at this point, as they have not been "saved" and are still unrepentant sinners. The problem is, even after they are saved and supposedly become model Christians, they still consider others' suffering an inconvenience. The only notes of genuine regret or contrition come from the supposedly un-saved.
They Wasted a Perfectly Good Plot: Done right, a story set during a Rapture-like event could have been quite potent character-driven Religious Horror, if the plot, the premise, and its implications were well-thought-out and the characters were sympathetic. Unfortunately, none of that is the case. The blog "Right Behind" functions as something of a Fix Fic for this, by taking some of the lingering queries about the world of Left Behind and exploring the implications of the setting to their logical conclusion.
You've got to hand it to Gordon Currie, who played Carpathia in the movies. He might have been a B-List actor in a B-List movie series, but he swung for the fences in every scene, making him perhaps the most engaging actor on the cast and portraying Carpathia as a far more intriguing villain than he ever was in the books.
Rayford is remarkably much more human and sympathetic in the movies, reacting reasonably to what is going on as much as the script allows and showing much more genuine loss and regret about his wife and child. Fred Clark sums up:
"On one side are Irene and Jamie, who are cheerful born-again Real True Christians. On the other side are Chloe and Rayford, who are portrayed by legitimate actors."
The implication that God Is Evil also comes from his tendency to torture people for eternity on purely religious (and not moral) grounds. Furthermore, since everything in the book is supposedly predestined, none of the people condemned to Hell had any choice in the matter. Depending on how much slack you want to give on His Omniscient Morality License, the series's version of God could range from being an anti-hero to a full-out The Bad Guy Wins. Not that the authors believe that, of course. See Values Dissonance below.
Verna Zee is intended as something of a Butt Monkey, a shrieking harpy who dislikes Buck whom Buck in turn stands up to and puts her in her place. However, given Buck's opinion of himself and Verna's motivation seeming to simply get him to do his job, Buck's treatment of her can seem rather unjustified and awful.
Carpathia himself to a degree, despite being the Big Bad and the Anti Christ. Early in the story he comes across as, at worst, a Well-Intentioned Extremist with emphasis on the "Well Intentioned". A lot of the main cast do a lot of judging of him internally, but given that the judgement has more to do with who he is than with the actions he takes, it can come across as unfair.
Unintentionally Unsympathetic: Irene Steele. '"Can you imagine, Rafe," she exulted. "Jesus coming back to get us before we die?"' She says this knowing that Rayford isn't all that religious a person. It's supposed to show how good a Christian she is, but it just makes her seem like she's trying to show off her faith to feel better than people who don't believe. She seems like the kind of person who says grace in a really loud tone of voice whenever she's at a restaurant just so she can feel superior to the other people there, who either don't say grace at all or do it in a reasonable tone of voice (or even say it silently). When Chloe is planning to go off to college on a scholarship and Irene is adamant that she stay and go to church with her (to the point of threatening to have Ray force Chloe into the car to go,) this is supposed to be a demonstration of Irene's care for her daughter and Chloe's ungratefulness. It comes across as Irene having no respect for her daughter's intelligence and growing independence.
Values Dissonance: The books are written with a particular religious demographic in mind as their intended readership. Said demographic has a very particular set of values, which are not necessarily widely shared outside of it.