In addition, the Kindle has become the most gifted item ever on Amazon, according to the company, which did not release sales numbers.
Amazon's peak sales day this year was Dec. 14, when customers ordered a record 9.5 million items worldwide, or 110 items per second. The news impressed investors who pushed Amazon stock up nearly 2% to $141 on Monday.
Amazon has never released sales numbers for the Kindle, but analysts say it is the market leader, with Sony's Reader a distant second. In general, e-readers were among the popular consumer electronics items in the holiday season.
Forrester Research predicts that 3 million e-readers will be sold this year in the United States. Next year, U.S. sales will reach 10 million units.
The popularity of the devices made it difficult for Barnes & Noble, which entered the market in October, to meet demand, despite mixed reviews for its Nook e-reader. The bookseller was forced to delay shipments, so Nooks bought after Nov. 20 were not expected to arrive until after the Christmas holiday.
Meanwhile, Amazon said it shipped to more than 178 countries over the holiday shopping season, with 99% of the orders arriving in time to meet holiday deadlines. Following the Kindle, the top-selling electronics were the 8-GB model of the Apple iPod Touch and the Garmin Nuvi 260W 4.3-inch GPS, respectively.
Among wireless devices, the leader was the Nokia 5800 XpressMusic unlocked phone, followed by the Plantronics 510 Bluetooth headset, and the BlackBerry Bold 9700 phone.
Overall, year-over-year sales at U.S. retailers rose 3.6% from Nov. 1 through Dec. 24, according to SpendingPlus, a unit of MasterCardAdvisors.