After announcing plans to start carrying Barnes & Noble’s Nook e-reader, Walmart is now adding another digital reader and will begin selling the Kobo wireless e-reader next week at 2,500 U.S. Walmart stores.

Kobo CEO Mike Serbinis said the Kobo reader has already been selling through Walmart Canada and the device (which sells for $140 through Borders.com) will “be the opening price in the e-reader category.” In addition to the Nook and now the Kobo reader, Walmart also recently began selling the Apple iPad.

On top of all of this, a number of tech sites such as CrunchGear are reporting rumors that next week B&N will introduce a full-color 7” screen Nook (the current model offers a black & white e-ink screen with a color navigational button) that will run on the Android OS and sell for $250. We’ll have to wait and see.