Amazon Kindle and Digital Books

I logged in to Amazon today and the announcement on the main page is that Kindles have been tough to keep in stock. I know that people are not reading physical books as much any more. I myself have been reading more digital documents and articles, but less physical books. I signed up for some free e-books to be delivered via e-mail to read on my iphone, but I still didnt have time to read them. Digital books seem more appealing as we culturally switch to a digital age full of ipods, blackberries, and other digital PDA's.