WARNING – This blog post contains math. I promise you it won’t include algebra or those blasted hard story problems from all our middle school nightmares. Let’s start with three numbers. 66. That’s the percentage of readers who prefer print books to digital eBooks. 635 million. That’s how many print books sold in the U.S. in 2014, an increase of over 3% from 2013 sales. 100. As in the number of print books that BookBaby publishing specialists recommend for first time authors. Why 100? You’re going to need them – and probably more.