When I was a newly published author, marketing to readers was mostly done blindfolded. Authors created swag to give away at events, to bookstores, and to libraries: branded pens, sticky notes, calendars, bookmarks, etc., and handed them out far and wide with no way to measure whether any of their efforts resulted in enough book sales to cover the cost of the swag. There was only cost involved, with hope of profit being made at some future time. Now we can measure the effects of our digital giveaways,...