Although the Holy Bible is a massive $2.5-billion industry, it is a bestseller that many Americans do not read much less understand, according to Christian scholar Jeremiah J. Johnston.

Writing for Fox News, Johnson said the Bible has been stripped down, twisted, misread, adulterated, supplemented, and even overruled. But despite all these modifications and reinterpretations, "95 percent of the congregation will not realise" them, he said.

The reason for this is that "many Americans no longer know the Bible," said Johnson, the president of Christian Thinkers Society.

The American Bible Society backed up Johnson's claim, noting the declining influence of the Bible in the U.S. its annual State of the Bible report.

Johnson noted the huge gap between personal opinions of biblical passages and their actual meaning. "Everyone has an opinion about the Bible. Politicians attempt to use the Bible, Grammy-award winners quote it and Hollywood has portrayed it on the big screen," he said.

"Yet one problem remains: most are oblivious to the Bible's basic content, meaning, and message."

For instance, "one-third of British parents thought Harry Potter was a thematic plotline derived from the Bible," Johnson said.

The Christian scholar said the "Bible illiteracy" in America cannot be blamed on lack of availability. "The Gideons give away a Bible every second. One publisher sells more than 60 different editions of the Bible," he said.

Johnson pointed out that the Bible is actually a "diverse love story" or "the greatest break-up-and-get-back together story the world has ever known."

"The message of the Bible is that even though we are not what we should be, God loves us, redeems us, and has a purpose for our lives," he said.

The Bible can also be described as "a tale of heroism, courage, persecution, betrayal and towering faith in a God who raises the dead, mixed through the centuries with the blood of martyrs," Johnson said. "If 80 percent of Americans believe the Bible is "God's word," shouldn't we show the Bible some respect by knowing more about it?"