Catholic writer Carl Olson was struggling as he led his audience through the maze of competing Christian beliefs about the Second Coming of Jesus.

There are premillennialists who believe Christ will reign for 1,000 years on earth. But it wouldn't be fair to lump them with the ultra-literal premillennial dispensationalists, he noted, since these camps contain bitter rifts over the timing of "the rapture." That's when the trumpet sounds, the dead rise and Christians soar to meet Christ in the air. Then there is the ancient amillennial stance, without a 1,000-year kingdom. Oh, and don't forget the postmillennialists.

Rows of middle-aged, cradle Catholics in Salem, Ore., gazed back -- utterly lost.

"I was getting absolutely nowhere," said Olson. "So I finally asked them: 'How many of you have ever heard a single sermon or even some kind of talk at church about what the Catholic faith actually teaches about the Second Coming?' There were 200 or more people there and four or five hands went up. That's what you see everywhere."

These Catholics didn't know their catechism. But, many could quote chapter and verse from another doctrinal source -- the "Left Behind" novels by evangelical superstars Tim LaHaye and Jerry Jenkins. This amazes Olson, who was raised in what he called a "strong, fundamentalist Protestant" home before converting to Catholicism.

The first 11 novels have sold around 50 million copies and that doesn't include the racks of children's books, audio editions, games, comics, DVDs and music products. Now the climactic "Glorious Appearing: The End of Days" is out, complete with a warrior Christ on a white stallion leading the angelic version of shock and awe.

The powers that be at the New York Times were struck by this scene: "Tens of thousands of foot soldiers dropped their weapons, grabbed their heads or their chests, fell to their knees, and writhed as they were invisibly sliced asunder. Their innards and entrails gushed to the desert floor, and as those around them turned to run, they too were slain, their blood pooling and rising in the unforgiving brightness of God."

For millions of modern Catholics, this is more exciting than the works of Justin Martyr, Augustine and the Second Vatican Council. Olson said it's hard to know what chunk of the "Left Behind" audience is Catholic, but publicists say that 11 percent is a good estimate.

This shouldn't be foreign territory for Catholics, said Olson, author of "Will Catholics Be 'Left Behind'?" In every Mass, they say they believe Jesus will "come again in glory to judge the living and dead." Catholics are taught -- along with Orthodox Christians, Lutherans, Anglicans and many others -- that "the rapture" will follow a time of tribulation and happen at the Second Coming, not seven years earlier as taught in the "Left Behind" series.

But it's hard to resist thrillers in which the mysterious Book of Revelation is decoded into visions of United Nations plots, global media, Chinese armies, Israeli jets and, well, Satan running the Vatican.

"Lots of Catholics tell me that 'Left Behind' can't be bad because LaHaye and Jenkins have the pope getting raptured along with the good guys," said Olson. "They don't even notice that this pope is considered a radical because he has started preaching what sure sounds like evangelical Protestantism. In other words, he's a real Christian. The next pope turns out to be Anti-Christ's right-hand man."

Meanwhile, most priests and bishops are silent, said Olson. Many fear being called "fundamentalists" if they even discuss issues of prophecy and the end times. Others may not believe what their church teaches.

The Catholic bishops of Illinois did release a "Left Behind" critique, claiming: "Overall, these books reinforce an unhealthy and immature belief in a harshly judgmental God whose mercy we earn by good behavior." But Olson said too many Catholic leaders refuse to take seriously the content of the books, movies and television programs that shape the beliefs of their people.

"If you want to be a good shepherd, you have to care about this stuff," he said. "These kinds of books and movies are where most Americans -- including Catholics -- get their beliefs and attitudes about faith and spirituality. ... You cannot wish these things away. They're real."