This Tennessean article has all the details.
From what I recall, before Patchett and her business partner, Karen Hayes, open their new Parnassus Books (and before the opening of a new Barnes & Noble store at/around Vanderbilt), Nashville was a large city without a bookstore to call its own. The Borders Books massacre and the closing of a huge Davis-Kidd bookstore there had left book buyers pretty much out of luck if they wanted to actually hold a new book in their hands before they paid for it.
NPR has even more details and pictures plus a link to an All Things Considered radio piece the network did on the opening of Parnassus Books.
And, finally, here is a direct link to the new store's website.