Twice Sold Tales has a few locations in the Seattle area. I normally stop by the one in Capitol Hill.
I checked out the store on University Way about a week ago and was surprised by the general disarray of the store. Books were just piled on shelves or tossed on the floor, it wasn't very clear where sections were located, and even the semblance of topic sections seemed to blend into one another. In general it made browsing or looking for a specific topic quite tough.
The prices are still good, even considering this is a used books store, and you may find a decent book among the clutter. Unfortunately, the general disarray, while possibly intended to yield a casual feel, does not lend itself to a enjoyable browsing experience.