2009 may be remembered in book circles as the year the e-book finally came of age. On Dec. 26, Amazon issued a press release with the headline, “On Christmas Day, for the First Time Ever, Customers Purchased More Kindle Books Than Physical Books.” According to the release, the Kindle Store includes some 390,000 titles, and Jeff Bezos says that the Kindle is now “the most gifted item” in the company’s history.

Of course, Amazon’s breathlessness comes with a minor caveat: according to Galleycat, as of Dec. 28, 64 of Amazon’s 100 top-selling e-books had a price tag of $0.00:

The number one bestseller was Midnight in Madrid by Noel Hynd, another free Kindle book. The list changes every hour, but these are fascinating and anxiety-producing statistics for publishers. With more than 60 percent of the one hundred most popular books in the eBook store priced at [$]0.00, how can publishers interact with this new readership and still earn money?

Galleycat links to an article from The Washington Post that provides some context for the ongoing debate over acceptable price points for e-books:

Macmillan recently announced a plan to delay the publication of e-books and offer enhancements that will justify a higher price. This tactic is aimed at Amazon’s policy of trying to set $9.99 as the expected price for an e-book. Most are priced much higher “ but that’s beside the point. Amazon and publishers are fighting over this fiction, not the reality. Because Amazon’s customers have made it clear that $9.99 is still too high for their taste. Most titles in the company’s list of top 100 Kindle bestsellers are priced below $9.99, and the most popular price point is $0.00. But publishers can’t hear this, because they’re a little distracted right now.

The Post article concludes by saying that if publishers want to thrive in the new digital world, they need to be open to lower-priced titles and higher author royalties (although $0.00 may be a bit too low a price point to stomach). Which may turn out to be one of the big stories in 2010. Stay tuned.