Powered by Kobo, several file formats are available including ePub and PDF. Not only that, but if you want some e-books but no e-reader, never fear because Borders already has you covered. You can pick up a Kobo, Aluratek Libre, or a Sony Touch or Pocket reader directly from the site.
Or you could just settle for the Borders eReader app for whichever supported device you already have. (It looks we'll be seeing these for Android and Blackberry soon too!) Otherwise, it's just your basic e-book store. Borders, however, does have some ambitions plans for the shop, including a goal to achieve "17 percent share of the eBook market by July 2011." Think they'll make it?