I think the growing trend for publishing technical books before they're complete and asking for feedback is really interesting, and I've found many books published this way that are affordable, timely, and high-quality.  That's one thing that interested me about the description of Steve Jalim's book on being your own boss:

Having gone that route myself over a year ago, I'm interested both in the insights that Steve has to offer, and in the ability to potentially contribute my own insights back to such a book. Check it out for yourself.