I'm wondering two things. First, do book giveaways spur sales, and, if so, to what extent?   Also, how about the buy-a-book, get-a-prize strategy? Through my national security reporting, I've accumulated a lot of spy gadgetry that I have no use for, pens that contain micro-video recorders, packofgumcams, water soluble paper, forged identity documents, etc. How might you use this stuff to induce r…