Apple's (AAPL) iPad is pulling e-reader market share away from's (AMZN) Kindle, according to a study released Tuesday by ChangeWave Research.

As the e-reader market has grown, Kindle's share has slid to 47% from 62% between Aug. 1 and Nov. 8, while the iPad's market share doubled to 32% over the same period, according to the report. The survey also indicated that people intending to buy an e-reader during the holiday season are about 25% more likely to purchase an iPad than a Kindle.

The report suggests that Apple may be threatening one of Amazon's top profit centers even as the company continues to grow. Amazon, the world's largest online retailer, posted a third-quarter profit that rose 16% as sales of electronics and other products, including Kindle, surged 68% from a year earlier.

And iPad sales appear likely to keep growing. In September, research firm In-Stat forecast that tablet-computer sales -- led by the iPad -- will more than double during each of the next four years. In its fiscal fourth quarter, which ended Sept. 25, Apple saw its earnings surge 70%, largely on sales of its iPhones and iPads. Specifically, the company sold about 4.2 million iPads for the quarter.

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