@ChrisBrown (How do u mention someone with a username that has whitespace?!).

Reward Mechanism. I've just started with LeanPub.com, not sure how it'll really work out. Ideally, I was hoping for LeanPub.com to somehow reward my readers for giving feedback about my books, which would be a great start towards "collaborative book-writing". It seems I have to reward my readers myself, with free coupons for my other books (which means I have to actually write other books as reward to readers giving feedback).

Talent Scouting. From these readers, there might be some who present higher know-how than me and my associates (who write these books). I would then rope in these experts, hoping that my books already meant enough work done to attract such experts into co-writing my books. Obviously, these experts may consider me too low in expertise, and may want to write their own books.

Start With Feedback. You could buy our books-in-progress and offer feedback. That's one way to collaborate with me on my books. If you have relevant expertise above my own, or perhaps around my own, I would then plead with you to co-write my books with me!