En route to a county fair last weekend, we stopped at the Martintown Grist Mill, both to explore the restored mill and to poke around the farmer’s market that sprouted up around it. While the mill itself was a charming piece of restoration, the real win of the day was in a battered cardboard box, placed carelessly on a picnic table with the word Free Sharpied across its sides. In it, I found a copy of Larry Niven’s Ringworld, which I understand to be a seminal piece of SF writing. I had never…