The tiny town of Spring Green includes a wonderful bookstore called Arcadia Books that I always visit while I'm there. I am never disappointed by their collection and I always leave with at least one (usually more) books.
The town also happens to be home to Taliesin, Frank Lloyd Wright's architecture studio and a current architecture school. House on the Rock is also located there (and plays a big part in Neil Gaiman's American Gods).
It's in the middle of nowhere, but the strange collection of attractions means there's a constant stream of people visiting. If you're ever in the Midwest you should definitely take time to visit! It's only about 3 hours from Chicago and even just seeing one of the plays makes the trip worth while!
A few of my reviews of APT shows:
APT photo from here, bookstore photos by me.