Books now may be free of ads but that could soon change with the increasing presence of e-books. The Wall Street Journal reports that as e-books grow in popularity, readers may find they are subjected to advertisements.

It may happen much sooner than some readers think. TMCnet reported that Google (News - Alert) eBooks started earlier this month.

In a blog post from James McQuivey of Forrester (News - Alert) Research, he predicted that such an innovation will lead to the “creation of an ad-supported publishing model.” Google has not advanced the idea, and it could meet with intense criticism from many in the publishing business, McQuivey admitted.

But he gives the cogent example of either Kohler (News - Alert) or Home Depot sponsoring the “browsing of a book on bathroom remodeling.” He also notes how advertising is the key source of revenue for most all other forms of media. But books historically were different. Readers purchased books. Books last, but as most ads age they become out of date.

But consider the new technology. Google will provide books from the cloud, McQuivey said, and “it can deliver ads that are timely and targeted.” He also foresees an economic model where, the more pages that are read, the more ads the readers see, and the more value raised for the publisher and author.

One example now in place is Wowio, which features up to three pages of promotional copy in e-books. Wowio explained on its website that it allows e-Books to be sponsored.

“Advertisers subsidize or buy the book for the reader,” said Wowio. “The reader tells their friends about their cool, new free eBook. The friends download their cool, new free eBooks. The advertisers expand their reach with a closer, one-to-one relationship with consumers.”

The Journal said a variety of advertising forms are being tested. Sponsorships are one idea. A second idea includes videos, graphics or text. They would feature a marketing message when someone starts to read a book or they could be placed along the border of digital pages. In addition, ads could be based on the book's content and/or target the demographics and profile of the reader, said the Journal.

There is definitely a growing market. The Journal reported that 7 percent of U.S. adults who go online read e-books. That percent is predicted to double in 2011. In addition, those who own an e-book reader, read as many as 40 percent of their books in electronic form.

Forrester Research (News - Alert) predicted that U.S. e-book sales are expected to increase from less than $1 billion in 2010 to more than $2.8 billion in 2015.