Apple (Nasdaq: AAPL) has always owned the nerds and hipsters. Now it's making a strong push for the bookworms.

The tech giant announced some pretty stunning statistics on the e-books front yesterday. Since the launch of its electronic bookstore, readers have downloaded 5 million books. That's good enough for a 22% slice of the e-book market, according to Apple's publishers.

Now, before we begin shrugging our shoulders at a 22% sliver of the nascent digital book market, or musing on how many of those 5 million books were public domain freebies, let's consider how remarkable an accomplishment this actually is.

  • Apple's didn't launch its iBooks app and marketplace until two months ago.
  • Until now, it has only been available on the iPad.
  • Apple has cleared a whopping 2 million iPads since its early April debut, but this still means that the average owner has downloaded an impressive 2.5 books.

If you're Barnes & Noble (NYSE: BKS) or Sony (NYSE: SNE), throwing in the digital towel doesn't seem like such a crazy idea at this point.

They're certainly not going to go down with a fight. Barnes & Noble recently rolled out a Nook app for Apple's iPad and is currently staging a promotion where even an iPad owner entering its store and running the Nook app can get a free cup of coffee.

However, the company that is now baking under the heat lamp is Amazon.com (Nasdaq: AMZN). It was the undisputed champ with its Kindle, and now Apple has become a major player overnight.

The competition will only get hotter from here.

Apple announced yesterday that iBooks will now be available in the next iPhone and iPod touch update. The software is also being upgraded, allowing readers to add new bookmarks, personal notes, and view PDF files. Kindle's customization advantages are no longer valid selling points.

This is huge. The iPod touch and iPhone may be small devices, but they have far larger installed bases. Apple expects to hit the 100 million milestone in iOS (the newly renamed iPhone OS) devices -- iPhone, iPod touch, and iPad -- later this month. If the iPad is 2% going on 3% of that mix, and was good enough to command more than a fifth of the e-book market, it may very well be the category leader by the end of the year.

Amazon can't let that happen. Its devices may be cheaper, its batteries may last longer, and its displays may be easier on the eyes, but it's still a one-trick pony when Apple is selling a Swiss Army knife.

The Kindle would need a color touchscreen or a fleet of word games to appeal to a broader market, or at least to the college textbook realm, but that doesn't appear to be coming anytime soon. All Amazon can do is get the word out. That's why it began selling its Kindle through Target (NYSE: TGT) over the weekend.

But the e-tailing giant can't stop there.

Amazon isn't the type to let pride get in the way of a good fight. It had no problem rolling out a Kindle app for the iPhone, despite the inherent limitations of the smaller smartphone screen. If Apple improves its product, Amazon won't sit out the arms race.

Unfortunately, Apple is already talking like a market leader. It even championed the agency pricing model for publishers.

The pages are turning quickly in this story, and Amazon is running out of papyrus.

Will Apple, Amazon, or someone else be the leading e-book seller in three years? Share your thoughts in the comment box below.

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Longtime Fool contributor Rick Munarriz has been shopping online for about as long as Amazon.com has been in business. He owns a Kindle and an iPad. He does not own shares in any of the companies in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.