Reza Aslan

Lagardére, parent company of book publisher Hachette, and Bertelsmann, parent company of book publisher Random House, both announced financial results for the first six months of 2013. Of the two, Lagardère provided more detail on digital results: Digital made up 11.3 percent of Lagardère Publishing’s net sales worldwide, compared to 8.4 percent a year ago. Ebooks now account for 34 percent of adult trade book sales in the U.S., compared to 27 percent last year, and 31 percent in the U.K., up from 22 percent last year.

It's a marketing triumph no book publicist or agent could have dreamt up: appear on Fox News, patiently endure a markedly confrontational line of questioning about one's religious affiliation, and wait for the whole thing to go viral.

But it's precisely what has happened for Reza Aslan, an Iranian-American scholar of religion, who appeared on a weekly Fox News webcast on Friday to promote Zealot, his controversial new biography of Jesus, only to be asked-repeatedly, for several minutes-why he, a Muslim, would be writing about Jesus.