Tech writers stuck with the unenviable job of working this past holiday weekend were blessed with a last-minute gift from Jeff Bezos: On Dec. 26, Amazon issued a press release proudly trumpeting the fact that on Christmas Day, for the first time ever, its online superstore sold more electronic books than regular books.This is certainly a milestone worth observing. Amazon has put out what critics have determined to be the market's best e-reader. And the company's transformation from hawking the wares of others to creating the "most gifted" product on its own site is impressive.But there's a simple explanation for why the Kindle's Christmas Day record isn't that impressive.If the Kindle sold as well as Amazon claims (and since they don't release specifics, we'll just have to take their word for it), then a lot of Kindles were under a lot of trees. Which meant a lot of people woke up Christmas morning with an immediate need to fill their empty Kindle with an e-book or two.Amazon is the only place you can buy Kindle titles, which can't be said for books in general. So what we have is a company with a monopoly on supply on the largest demand day in history.A nice record, for sure. But perhaps unsurprising given the circumstances.