The Association of American Publishers announced Friday afternoon that net book sales went down 0.3 percent in April, but the industry could still boast of a 6.3 percent increase in year-to-date sales compared to the first four months of 2006. Based on what we’ve seen from the numbers in January and February, plus the fairly stagnant numbers in March (which I was sure I blogged about, but my archives are telling me different), and I think we can safely predict a PW article on how bookstore sales were down for the month ’round about week’s end…