I agree that people read far less BOOKS than they used to, but isn't that largely because of our busy lifestyles, our growing love for modern 'new media' alternatives etc?
Isn't that the point of these mac computers, to gel everything that you need, and put them all at your fingertips? I think it is less about people not reading, and more because people aren't used to the whole concept of purchasing digital books online...yet. iTunes store will never make the kind of sales on books that they do with music.
The problem is you can't sell books to any generation of people in the same glittery way as you can blockbuster movies.
I do think you could gradually get consumer interest going by providing a digital link & code system on every paperback book in Borders for example, meaning that you have purchased the book and the link to download it for viewing on your tablet if desired.
I can see that the the many creative pros and pro-sumers would gain from having the kind of touchscreen tablet that would allow them to tweak their digital creations without the need of a wacom tablet. To be able to have all the features of every other mac in your lap, as light as a macbook air, a tablet would have all the convenience of reading a magazine, easy to pick up, easy to put down, easy to pass around and doesn't make you look as if you've brought work along with you wherever you go. Be a hardcore user, do seriously amazing stuff, but the chance to appear casual about it, instead of a computer geek.
I think a multi-touch, touch screen tablet form mac would be huge. The Macbook Air minus the keyboard would be a great start.