Last week, Digital Book World editorial director Jeremy Greenfield shared the details of an interesting (if non-scientific) e-reading study; it was conducted via DBW’s Twitter account, which has more than 20,000 followers.

The tweet itself was simple enough; it read this like: Do you read on your smartphone? Do you read on other devices, too? Tell us!

As of September 11, 30 DBW Twitter followers had answered back, and about half of those respondents answered in the affirmative. The tweets featured in the post were fairly interesting, although most surprising to me was Greenfield’s mention of Michael Tamblyn, Kobo’s EVP of content, sales and merchandising: In a DBW interview conducted earlier this summer, Tamblyn said that he reads almost exclusively on his iPhone. (It’s a fantastic interview, by the way; click here if you’ve got an extra 20 minutes to spare.)

You’ll also find some rather telling smartphone stats in the DBW piece, including these:

According to a new study, 45% of all U.S. adults now own a smartphone, about double the proportion that own dedicated e-readers or tablet computers, currently making smartphones the most common mobile e-reading devices.

The proportion of young adults (18 to 29 years old) who own a smartphone is even higher, with two-thirds owning one, according to the new study from the Pew Internet and American Life Project. Almost the same proportion of U.S. adults aged 30 to 49 year own a smartphone (59%).

With fewer e-book buyers gravitating toward dedicated e-readers as their reading device of choice, tablets, smartphones and other e-reading venues will become more important for publishers to pay attention to. According to two other Pew studies, in the earlier part of this year, about one fifth of U.S. adults owned an e-reader and about the same proportion owned a tablet computer.

Greenfield also points out something that many of us here probably already know: The fact that tablet ownership numbers are being projected to go through roof in the near future: Worldwide, as Greenfield writes in an August 30 post, “about 102 million tablets are set to be shipped to consumers in 2012, while that number is 11 million for e-readers (down from 15 million e-readers in 2011.) In 2017, the number of tablets expected to ship globally is 250 million.

And yet, “just because a consumer owns a tablet computer or smartphone doesn’t mean they will read books on it,” Greenfield adds.

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The following reading-habits statistics come from an April Pew study:

– 42% of e-book readers consume their books on a computer
– 41% of e-book readers use an e-book reader like original Kindles or Nooks
– 29% of e-book readers read books on their cell phones
– 23% of e-book readers read books on a tablet computer

Did you catch that? According to the Pew study, 29% of e-book readers use their cell phones to read, while only 23% read on tablets. That’s almost difficult to believe, although when you consider the growing omnipresence of smartphones, I suppose it makes more sense. There are certainly a lot more smartphone owners out there than tablet owners.

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“Publishers are already thinking about new ways their content can and should appear on tablets,” Greenfield writes. “Perhaps they should be taking a second look at smartphones, too.”

Personally, I couldn’t agree more. I’ve read—or attempted to read, as the case may be—with four different apps on my smartphone, which runs on Android’s 2.3 (Gingerbread) OS. Interestingly, I’ve found the Google Play Books app to be nearly useless. It’s a little tough to explain the app’s shortcomings to someone who hasn’t used it, but it almost seems as if Play Books’ overarching goal is to prevent users from reading at all.

As for the Nook and Kobo Android apps, I probably haven’t spent enough time with either one to offer an authoritative opinion. What I can say, however, is that the Kindle Android app seems to have them all beat. At this point, it’s the only app I use when reading on my phone, and I doubt I’m alone in that.

Of course, my own phone-reading preferences may vary widely from yours, and that’s why I’m interested in hearing about them. If you have time to leave a comment, here’s what we’d like to know:

1. Do you read e-books of any sort on your smartphone? If so, do you tend to read full-length books, or do you find yourself instead reading articles and Kindle Singles and the like?

2. If you are a smartphone e-reader, what are you app preferences (assuming you’ve tried more than one)? Have you discovered any tricks that have improved your phone-reading experience?

3. And finally, when and why do you find yourself reading on your phone? For example, I like the fact that when I’m in public, my phone is almost always withing arm’s reach—in fact, it’s usually in my back pocket. That means I can read while waiting in like at a grocery store, for instance, or even during a long rush-hour elevator ride at the office.

On a slightly less specific note, if  you have any ideas about how the smartphone reading experience could possibly be improved upon, we’d very much appreciate hearing them.

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Chart | The Rise of E-Reading | Pew Internet and American Life Project