In the fourth quarter of 2010 (Q410) 10.1 million tablets shipped, more than double the 4.5 million shipped in the third quarter, according to a new report from IDC.

Apple’s share decreased from 93 percent in Q310 to 73 percent in Q410, but still showed its solid leadership position. The Samsung Galaxy Tab was the main competitor during the holiday season, accounting for more than 17 percent share.

IDC found that the eReader market also increased significantly in the fourth quarter. Strong sales of Amazon’s Kindle, as well as significant gains from competitors such as Pandigital, Barnes & Noble, Hanvon, and Sony among others, contributed to market growth.

In Q410, the eReader market more than doubled volume from the previous quarter, with more than 6 million units shipped for the quarter, bringing the full-year total to 12.8 million units shipped. eReader shipments were also up more than 325% from 2009 when roughly 3 million units shipped.

“Strong holiday sales of media tablets were in line with IDC projections and strong consumer interest in the category while device vendors scrambled to offer products competitive with Apple’s iPad and now iPad 2,” said Loren Loverde, vice president, Consumer Device Trackers.

“Media Tablets are on pace to reach shipments of roughly 50 million units in 2011.”

According to IDC, the United States, Western Europe and Asia/Pacific (excluding Japan) regions accounted for 89% of all media tablet shipments in 4Q10. Although the United States remained the largest country market, Western Europe and Asia/Pacific (excluding Japan) grew almost twice as fast from Q310 to Q410 and Western Europe saw a slightly larger jump in shipments in 4Q10.

In Q410, retailers were the channel with the highest share of shipments, followed by direct and telco sales. A new channel for media tablets, the telco operators, accounted for nearly 14% of all shipments of media tablets in 4Q10