eback
(n.) -- an e-book composed in or converted to a digital format for display on a computer screen or handheld device; first there were hardbacks and paperbacks, now there are ebacks
"I just ordered Stephen King's latest novel in digital format. For me, an eback is just as a good as a paperback book, even better, because I can store it for use anytime anywhere and read it off a variety of screens."

-- overheard at a watercooler in a bookstore in Chicago on March 24, 2010