Atria Books e-book vouchersWe've reported a number of times over the years about small start-ups that are attempting to solve the quandary of the author autograph in the digital age. A reader attending an in-person author appearance and hoping to walk away with a signed book, for instance, is clearly out of luck if she happens to only own the electronic version of the writer's book. And so companies like Autography and Kindlegraph have devised some pretty unique solutions. But autograph collecting is an obscure hobby. Aside from the novelty aspect, it's not likely to interest many of us. A company known as Impact Mobile, however, recently teamed up...