Have you ever heard you can use your book as a business card? That is the general consensus with those who work with authors in any manner.
Most authors want to get their message out into the world and have no other basic desire except to speak to groups about what they have written about. When an author gives their book away to an audience, they are able to build a following of those interested in who they are and what their message is.
Often when authors are speaking, the event planner will prohibit selling to the audience, so giving the books away in exchange for the name and email address is more than a break even proposition.
Almost everyone will value the name of a new person in their database because they know the return is an average of $10 a month. And that is just the beginning. When you are able to build a database of interested parties, you will find they will bring you years of financial returns.
There is the purchase of audio programs, future books and even participation on your membership site that will have your bringing in income for your intellectual property. It goes well beyond your book.