There aren't many of us around these days who remember all the old time used bookstores in Detroit, but I remember the Big Book Store. They've been around forever. Now it's mostly old magazines and comic books and sports cards. The books aren't much, but it is fun to poke around on the dusty shelves and find something no one has looked at in 20 or 30 years. Bill, the manager, is fun to talk to and knows everything in his store. Not for the faint of heart though: they do have adult material (in a separate area)
John King Books is enormous, the biggest in the area (750,000 books!) and one of the biggest in the country. And, their prices are cheap. Don't expect them to be able to tell you if they have a certain book over the phone (they're too big) but a visit is worth the trip, big time!
I like the environment for the most part. The staff is friendly and the prices are fair. But there is a Jamaican guy that walks around and harasses the booth users and makes people feel uncomfortable. Weekends are better because he doesn't work on those days.