1) put your book in the permies.com digital market. This will be a pdf file. We have a built in mechanism to get a copy to each person it is supposed to go to. Just send us the pdf and we will get everything set up from there.
2) your book is already on amazon. We will tag your stretch goal with "Note! You must claim your ebook within a 48 hour window!" This is what we have worked out with Michael Judd and his book "Edible Landscaping with a Permaculture Twist". When the time approaches, we will alert the recipients several days ahead of time that a window will open on a certain date and time and they must grab the book during the window or they won't get it. When the time comes, Michael will start a "free promotion" for the book. This does mean that during this time, anybody can get the book. But then the window suddenly closes. This is, apparently, a favorite marketing tactic for people on amazon. When people realize that they missed the window, they still buy the book. Sometimes, tens of thousands of people then buy the book.