So what about my claim that readers downloaded 15 million Kindle books, 10 million of them paid, in the last week of 2010? Actually, those figures are conservative, despite the fact that my friend and colleague Morris Rosenthal (who brings a lot to the table where statistical estimates of Amazon sales are concerned) puts the figure at 3 to 3.5 million.

There are some important numbers that I cannot share here because they involve confidential information concerning my own sales figures and figures that have been shared confidentially with me by other authors and publishers, so let’s take a different approach. We’ll call it “common sense,” and there are several different ways we can come at this. Let’s start with something we got from the world of the Nook:

• Barnes and Noble issued a press release on December 30 saying both that it had sold “millions of Nooks” so far and that customers had downloaded “nearly one million NOOKbooks purchased and downloaded on Christmas Day alone.” So we can extrapolate that on Christmas Day alone there was at least one ebook sold for every three Nooks.
• We begin with the expectation that there were 11 million Kindles by December 25, but let’s say that 1 million of those were secondary Kindles, defunct Kindles, etc. On the other 10 million Kindles, assuming that Kindle owners are every bit the active readers that Nook owners appear to be, that would lead us to conclude that they downloaded 3.3 million Kindle books on Christmas Day alone. 
• Amazon stated earlier that about 20 percent of Kindle books are downloaded to Kindle apps on other devices. While Kindle device sales were certainly brisk ahead of Christmas, so were sales of all the other devices that run the Kindle purchasing and reading app. Thus it makes sense to stick with the 20 percent figure for Kindle purchases on other devices, and if we do the math, that would come to 825,000 Kindle books downloaded on other devices. Let’s round it down to 4 million. Yep, that’s 4 million Kindle books purchased and downloaded on Christmas Day.
• While the annual rush period for print book publishers, retailers, and authors runs from Black Friday to Christmas Eve, it’s a very different calendar in the ebook business. Sales peak on Christmas Day and hold at very high levels through the first week of January as people open new ebook readers. On December 25, 2009, I sold over 1,700 copies of my bestselling ebook, which was more than 3 times my sales on any previous day. But that ebook’s daily sales did not slip below 1,000 copies a day on any of the next 10 days. That experience runs parallel to what I have witnessed but cannot disclose about dozens of other ebooks by other authors, so that I am confident that if Amazon sold 4 million Kindle books on Christmas Day, its sales for the following 6 days did not slip below 2 million copies a day, for a total of over 16 million Kindle books sold during the final week of 2010, and the figure is probably higher still by a million or more. Even if a third of the downloaded Kindle books were free, that still comes to over 10.5 million paid Kindle books.

Or here’s another way to look at it, and we start again with the 11 million Kindles figure as of Christmas morning:

• That figure includes 4 million previous-generation Kindles that were shipped by July 2010 and another 2 million Kindle 3s that were shipped prior to Labor Day. Let’s say that no paid ebooks at all were purchased on a million of those units during the last week of 2010, and that only an average of 0.5 ebooks were purchased that week on the other 5 million units. So there’s a very conservative start, with 2.5 million paid ebooks sold on those ancient Kindles.
• Then let’s take the 5 million new Kindles shipped since August. Let’s say, again, that a million of those weren’t used to download a single ebook for the final week of 2010. On the other 4 million, let’s hypothesize something like this:

• 1 million units downloaded 0.5 books each (0.5)
• 1 million units downloaded 1.0 books each (1.0)
• 1 million units downloaded 2.0 books each (2.0)
• 1 million units downloaded 3.0 books each (3.0)

• That comes to 9 million paid ebooks loaded directly to Kindles, and that would suggest 2.25 million ebooks loaded to Kindle apps on other devices, for a total of 11.25 million.
• Again, I believe these models and the results of 10.5 to 11.25 million paid Kindle ebook sales for the last week of 2010 are conservative, because, for one thing, I believe that about 3 million Kindles were opened for the first time on or about Christmas Day and it would confound my understanding of human nature to think that, in the hands of people who love to read, those newly unwrapped Kindles led to only 6 million ebooks downloaded. I just don’t see many of those folks saying, “I can’t wait until Monday morning so I can go to the public library to find something to read.”

We could go on and on, but I sense that your eyes have already long since glazed over. Again, it doesn’t really matter if there were 11.25 million paid Kindle books sold during the last week of 2010 or 9.7 million, but we can be quite sure that the figure was far north of 3.5 million.

I have no doubt that there will be a few publishing industry insiders who read this post and conclude once again that I’ve been drinking that Kindle Kool-Aid again, and that I am totally caught up in the hype of the so-called “Kindle revolution.” They will point out that everyone knows that ebook sales are really only 8 or 10 percent of the trade book market.

To which I say, yep, it’s apple-flavored Kool-Aid and, well, how do you like these apples? … as reported today by Bob Minzesheimer and Craig Wilson in their USA TODAY Book Buzz column:

E-books surge: Egads, as cartoon heroes would say. E-books had another great week after up to 5 million digital reading devices were unwrapped for the holidays. Last week, the e-book outsold the print version for 18 of the top 50 books on USA TODAY’s Best-Selling Books list, including all three Stieg Larsson novels. The week before, 19 had higher e-book than print sales. That was the first time the top 50 list has had more than two titles in which the e-version outsold print.