"The Purpose-Drive Life" is current example
A current example of the cross-over appeal of Christian books, he said, is "The Purpose-Driven Life" by Rick Warren. That book has been No. 1 among all genres of Christian books for 27 weeks and is a national best-seller in the secular market.
"The book not only has attracted millions of readers across the spectrum but it also has been the foundation for a lot of special sermons and programs in churches and for discussions by non-religious groups involved in counseling programs," McClelland said. "In the churches, pastors have used the book as the basis of series of sermons, and the book has been the topic for many Sunday school programs.
"The book seeks to promote spiritual growth and develop faith-based ministries, both on an individual and a corporate or collective basis," he said. "While it is absolutely Christian in its message and approach to life, it has a general appeal to all people who are looking for a purpose in life, at least a purpose to do good for one's family and community."
A series of books by Max Lucado has had similar cross-over appeal, McClelland said.
"Max Lucado's books also are about Christian living and how to make the best out of life and do the best in your life," he said. "His work teaches us how to live every day of your life and how to identify the major problems in your life and how to work to solve them based on Christian ideals and principles and the blueprint established in the Bible.
"While the foundation of (Lucado's) writing is clearly Christian faith, it offers all people suggestions for how to deal with everyday life and how to work on everyday problems."
An extra boost from "The Passion of the Christ"
McClelland said Warren's and Lucado's books in the Christian living genre have been given an extra boost because of the huge popularity of the movie "The Passion of the Christ."
"That movie has caused many people to rethink their approach to life, to respond to a higher calling that involves being more in tune with the needs of others, to be less selfish and more giving," he said. "It tells us that, given what Christ did for us, occasional, much less violent sacrifices should be the least we should do. The movie tells us to forget the little, petty things that distract us from much more important matters."
In the inspirational category, a popular cross-over book is "The Faith of George W. Bush" by Stephen Mansfield, said McClelland.
"The book tells how the president's faith is reflected in his responses to various crises and situations, including 9-11 and the war in Iraq," he said. "The book is popular among Christians because of the president's very public Christian faith, but it also has attracted many other readers because it shows how the most powerful man in the world makes decisions and also offers some biographical information on the president."
In the general fiction category, one of the most popular series of Christian books in any genre and one of the top cross-over series ever is one by authors Tim LaHaye and Jerry Jenkins, said McClelland. Called the "Left Behind" series, referring to first of the 12 books in the series, the LaHaye-Jenkins books deal with the "endtimes" and the "seven years of tribulation," he said.
"Left Behind" was published in 1995, and more than 8 million copies have been sold since then, making it one of the top sellers of any kind of book in the history of publishing, not far behind the first of the "Harry Potter" books/.