This combination of file photos shows the 7-inch Amazon Kindle HDX tablet, left, and the Samsung Galaxy Tab 4 Nook. (AP Photo/Ted S. Warren, John Minchillo, File)
This combination of file photos shows the 7-inch Amazon Kindle HDX tablet, left, and the Samsung Galaxy Tab 4 Nook. (AP Photo/Ted S. Warren, John Minchillo, File)