I recently interviewed Len Edgerly, a former business journalist and executive in the energy industry who is now the host of some of the most widely followed podcasts in the e-reading industry, including The Kindle Chronicles. We discussed how the Kindle matches up with Apple's (Nasdaq: AAPL) iPad, as well as other players in the e-reading space. What follows is an edited transcript of the interview.

Chris Hill: Amazon (Nasdaq: AMZN) isn't releasing specific figures on how many Kindles have been sold. What is your sense of where this is in terms of Amazon's business?

Len Edgerly: In terms of the number of Kindles that they have sold, I think that by the end of this year, they'll have sold 5 million of them since they started. That would seem about right and so that, if you do the arithmetic, that is not really a huge proportion of sales for Amazon. The book sales probably are more significant, but even that is a sliver at this point. The exciting thing about it I suppose from an investor's point of view is where it ramps up to.

I think the way to think about that is I believe there are 30 million people in the U.S. who read two or more books a month. At this point, e-books are just a small portion of that. But because people who read that seriously are pretty likely to gravitate toward these devices, especially as they improve, then you get to probably having most of those 30 million people reading on e-books. So if e-books are accounting for 5% of the total books now, maybe they are up to 20% in two years.

Forrester just did a survey at the end of May of 4,000 individuals, which gave them, I think, their best handle yet on actual market share, and they are pegging the share of Kindle device sales at about two-thirds of the market. And I don't really think that that is going to change. So if the adoption goes, of these, people that read two or more books a month fills out and Amazon has got 70% of it, that probably does end up becoming a significant number for investors.

Hill: Let me get back to the heavyweight battle, which is Kindle versus iPad. What do you think is the biggest untapped opportunity for each one?

Edgerly: I think for iPad, the whole idea of enhanced books is something that I don't really have my mind around yet as a reader. But with enhanced books, if all of a sudden it is way better to be able to hear the author read a passage and "click here to see a video of this place in Europe that the story is about," I don't know what it looks like, but if there is sort of a book 2.0 that relies on those kinds of capabilities, the iPad is clearly going to wipe the Kindle in making it possible.

I think the iPad has got much better hope of kind of taking over the magazines and the newspaper area. It is so much fun to just be tapping your way around that magic screen and the newspapers I love because you are reading a story and then you are tapping on a video. All of a sudden you are in the newsroom, and these really smart reporters are talking to you in videos so that you are not sort of being taken out of the newspaper, you are sort of diving deeper into it in a way that I think really works.

The Kindle opportunities I think have to do with great new ways to connect with people who write words. I am thinking of the crowd at The Atlantic, James Fallows and people that are just great writers and banging out a really significant piece of writing about a current topic. If they're able to just jam it out to the Kindle the next day so that people can subscribe to it or they can buy it or whatever, then you're getting different lengths of writing being developed because there is this new way for serious readers and long-form readers to read them.

I guess that is how I would see it. The divergence would be Kindle getting better and better at actual text and words and then the iPad having a pretty clear advantage on things, in addition to words, which are still going to be pretty neat to have as part of the content.

Hill: Do you think one of them is better positioned than the other when it comes to the educational market? Is one of them really well poised for textbooks, or is there no clear advantage?

Edgerly: Well, I would have to give the edge to the iPad because I can picture carrying that around in your knapsack and you have got your textbooks. You can do all of your other things, and it has been a long time since I have read a textbook, but I assume that there tends to be more graphs and things like that that are better suited to the iPad platform.

The thing that I am finding is it is a completely natural process for me to have both, particularly when I am traveling. I have got a little cloth bag I carry with me. I put the iPad in it and I put the Kindle in it with a nice, slim leather cover, and I have got everything I need.

It doesn't feel like I am bringing the same thing twice; it feels like I am bringing the thing I am going to use to check my email and Twitter and all the iPad stuff and read the Financial Times. Then I am bringing the thing that I am going to use when I sort of unplugged. It helps to have that immersive reading device be a different thing, because I am sort of putting the computer aside and then I am turning to this more book-like, iconic thing. My body and mind are both agreeing to take a break and to go into material that is really pleasurable to read in a more focused way, without the temptation to press a button and see how many replies I have got on Twitter in the last 10 minutes.

To find out why size matters to e-readers, read Part 1 of my interview with Len Edgerly.

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Chris owns shares of Amazon. Apple and Amazon are Motley Fool Stock Advisor recommendations. Try any of our Foolish newsletter services free for 30 days. The Motley Fool's disclosure policy also has a crush on the "It's a Kindle" woman in the Amazon commercial.