I'm often laughed at when I suggest it, but I think the publishing world needs to look at what's happening with free to play games. You remove the barrier to entry so that as many people as possible will try your product (free). You identify those people who really enjoy your book and want to consume more of the same. You provide them with so much content that they can spend as must as they like. It's not unreasonabl…
The jury's still out on how successful it will be, for what kinds of projects, but I think it's clear that the world in which $15 retail packages are the only form factor prose fiction is ever sold in is basically gone, and that's probably for the better.
My favorite early example of this was Shadow Unit (http://shadowunit.org/), an entirely donation-supported serial.