David Bromley, a religious studies and sociology professor at Virginia Commonwealth University, said the U.S. has historically been an exception in a more secular world.
"There is a kind of historical strength to an 'In God We Trust' kind of generic religion, which some sociologists call civil religion," Bromley said. "That belief that America is a city on a hill, God's chosen nation, the flag and God being connected -- those kinds of things have a historical rooting. So when you ask people, 'Do you believe in God?' It's almost un-American to say 'no.'"
He said it isn't surprising that books on heaven and angels succeed in our culture.
Still, while "Heaven Is for Real" remains a publishing phenomenon, it has also attracted some criticism.
In March, author and Washington Post on Faith blogger Susan Jacoby wrote, "Only in America could a book like this be classified as nonfiction."
Pointing out the difference in the book's placement on Amazon book lists in the U.S. and the U.K., she said the book's commercial success attests to the "prevalence of unreason among vast numbers of Americans."
"In this universe of unreason, two plus two can equal anything you want and heaven is not only real but anything you want it to be," she wrote. "At age four, the inability to distinguish between fantasy and reality is charming. Among American adults, widespread identification with the mind of a preschooler is scary."