If I were to tackle the book business, I'd like to try something like that: ebooks plus an on-demand printing service for those that like their physical books :) .

I don't know if there's a good binder for such a service, but I've been demoed some very impressive printers at very cheap per-page prices on loan.

The real problem, of course, is securing the copyrights and the right to print or resell the books.