While converting former industrial space into luxury lofts has become the hallmark of hipster gentrification, John King was hip to the jive long before. Back in 1983, King bought the abandoned, four-story Advance Glove factory in downtown Detroit, thinking it would be suitable for his book-selling business. Fast forward a few decades, and the former factory now holds more than a million used and rare books. And so excellent is the collection, that earlier this year Business Insider named it one of the best must-see bookstores in the world. It may look a little rough-and-tumble on the outside, but we know you'd never judge a book by its cover.