Leo Babauta’s Focus. He writes:
This is the beta, online version of my second book, tentatively titled: focus – A Simplicity Manifesto in the Age of Distraction.
I’ll be drafting this book online in various stages (or versions), using the Gmail software model.
This is a radical new model for writing books. I’m not sure if it’s been done this way yet. It’s a form of Radical Transparency.