When Apple unveiled its iPad in January with its full-color high-resolution glory, many assumed it would be end of story for Amazon.com's Kindle book store and its black-and-white reader.

Turns out the iPad has actually helped Amazon. Not only are sales of the Kindle device expected to grow 140% this year to nearly 5 million units from 2009, but digital book sales via the Kindle store are on track to grow 195% to $701 million in 2010, according to Cowen and Co., which released a report Monday on the digital book market.

Greasing those book sales are Amazon's Kindle app for iPhone and iPad, which are the digital equivalent of little storefronts that let customers browse, buy and read digital books on those devices. In other words, you don't have to have a Kindle device to buy a Kindle book.

In fact, one in five people who buy digital books from the Kindle store don't own a Kindle device, according to Cowen's survey.

The "iPad is not having a negative impact on Kindle device or e-book sales," according to the report, written by Cowen analysts Jim Friedland and Kevin Kopelman. "In fact, we think the adoption of tablets will boost Kindle e-book sales."

Of course, iPad owners who read digital books tend to use Apple's iBooks app, which is linked to Apple's iBookstore, a direct rival of the Kindle. Nearly 60% of digital book readers on iPad report using iBooks most, but Kindle follows closely with 31% who say they use it most often, according to the Cowan survey. Among hard-core readers who go through 25 books or more a year, 44% prefer using Kindle on the iPad, compared with 47% for iBooks — virtually a dead heat.

For 2010, Cowan estimates Apple will have 5% of the market for digital books, compared with Amazon, which is projected to have 76% of the market. But by 2015, Cowan estimates Amazon will have 51% of the market and Apple with 16%.

So it seems we're into only the first chapters of the e-book wars, with more plot twists to come.

Corrected: This post has been corrected to reflect the accurate percentage of iPad owners who say they use Apple's iBooks most (nearly 60%) compared with 31% who said they used Kindle most.

— Alex Pham

Photo: Apple's iPad. Credit: Jay L. Clendenin / Los Angeles Times