That's a toughie. I'm very philosophical, so I'd probably write a book on a philosophy of mine (assuming no one else has come up with a philosophy called "neutralizationism") or I'd write a medieval/steampunk adventure. Medieval/steampunk is a genre like Final Fantasy VI; people still use castles, swords, spears, and bows, and they still ride animals for long-distance transportation, and armor is still necessary during battle. However, slightly advanced technology is available; for exmaples, people may use primitive trains, primitive firearms, early blimps or aircraft, and primitive submarines to name a few. It can make for some very interesting stories to tell.