Amazon.com Inc. (NASDAQ:AMZN) announced that its third generation Kindle e-reader is now the bestselling product in its history, surpassing Harry Potter 7.

On Christmas Day, the company said more people turned on new Kindles for the first time, downloaded more Kindle Buy Once, Read Everywhere apps, and purchased more Kindle books than on any other day in history. On the peak day this season, Amazon's worldwide fulfillment network shipped over 9 million units across all product categories.

Kindle's $139 price point is a key factor -- it's low enough that people don't have to choose, said Jeff Bezos, Amazon.com founder and chief executive officer.

Bezos said many of the people who are buying Kindles also own an LCD tablet. Customers report using their LCD tablets for games, movies, and web browsing and their Kindles for reading sessions.

They (customers) report preferring Kindle for reading because it weighs less, eliminates battery anxiety with its month-long battery life..... and works outside in direct sunlight, an important consideration especially for vacation reading, said Bezos.

The Seattle-based company also said customers ordered more than 13.7 million items worldwide across all product categories on its peak day, Nov. 29, which is a record-breaking 158 items per second.

Shares of the world's largest online retailer ended Monday's trading at $182.14 on the NASDAQ.