Since the beginning of 2010, the NIV Bible and NIV Study Bible have been among the top five e-books in the Religion & Spirituality category of the two popular e-book stores.

"A growing number of consumers are adopting the e-reader format, whether it's the Amazon Kindle, the Apple iPad, Barnes & Noble Nook or Sony Reader," said Chip Brown, senior vice president and publisher for Bibles at Zondervan. "Many of these consumers are purchasing an e-Bible so they can have the Word of God in an easy-to-use digital format. We're encouraged by the success of our e-Bibles to date, and remain committed to offering consumers the content and features they want in the format they desire."

E-Bibles now represent more than 40% of the company's e-book revenues, and in several instances they have outsold some traditional hardcover Bible products, Zondervan officials said. From mid-May to mid-June, the NIV Study Bible for Kindle sold more units on Amazon.com than the hardcover edition.

The first publisher to have Bibles available in the iBookstore with the launch of the iPad, Zondervan has published more than 15 Bible titles for e-book readers and currently has 1,450 books and Bibles available in the e-book format across the various platforms.

At the end of May, the Association of American Publishers reported that in the first quarter of 2010, overall e-book sales showed a year-over-year increase of more than 250%.