What with a public library in nearly every neighborhood and countless classics online — let your co-workers think you’re examining spreadsheets when you’re actually devouring Moby-Dick— it’s fair enough to wonder why anyone should ever spend even a penny buying anything to read. But for those whose taste tends toward the tangible and those who live to own, stocking bookcases can really add up. Full-price is for fools; new is for numbskulls. At library book sales, dinged-up castoffs mingle with nearly-new donations to fill table after table at rock-bottom prices, with proceeds going toward a good cause. Most libraries have sales only once or twice a year, but the Friends of the Lafayette Library host sales on the first and third Saturday of every month at the Lafayette Community Center, 500 Saint Mary’s Road, boasting books in nearly two dozen categories, from Westerns to foreign language to theater.