And then there's the problem of how to have an author sign a digital book. Robert Kiyosaki, author of bestselling personal finance book "Rich Dad Poor Dad: What the Rich Teach their Kids about Money - That the Poor and Middle Class Do Not!" and, most recently, "Unfair Advantage: The Power of Financial Education", had begun to encounter people at book signings who handed him their Kindle to autograph, and he wasn't sure what to do about that.