What kind of sissy phonebooks were you using?? I took a box that was approximately 8"x8"x16" and stuffed it with phonebooks and cardboard. The first 3 inches was phonebooks, the rest was just a bunch of layers of cardboard. I shot it with a 10/22 from 25 ft away 10 times and none of the 40gr .22LR bullets made it more than 10 inches. Maybe cardboard is more bullet resistant than we give it credit for?

Either way, if the books still have relevant knowledge or wisdom in them, shooting them is the last thing you should do.