One day, the year 2012 may be remembered as the year of the multimedia tablet device. At least five companies—Amazon, Google, Barnes & Noble, Kobo, and Microsoft—have released upgraded or new tablet devices, all aimed at competing with Apple’s iPad, the undisputed king of the tablet computing realm. Indeed Apple also released a new device—the iPad Mini. Once again, tablets and digital readers are poised to dominate holiday gift giving, thanks to a marketplace crammed with reasonably priced, high-performance devices. Here is a chart of the most popular tablets that offer consumers a place to read e-books and other content.