Square One Books
4724 42nd Ave SW
Seattle, WA 98116
206-935-5764
This all-new bookstore in West Seattle is ten minutes from Downtown. It’s been around for 22 years and has been voted West Seattle’s best bookstore. It’s in a strip-mall, but the location is great and there are a lot of people walking around.
Square One isn’t a large store, but it is supported by the West Seattle community and the folks at Square One Books know their customers well. They pride themselves on being able to talk to their customers about books and serving them as well as they can. They even provide free delivery! 
All and all this feels like a strong general trade bookstore. They carry a lot of different titles, and they know how to provide quality service to their customers.
I like your project and it’s been fun reading the entries, especially the local (Seattle-area) ones. However, you will be doing yourself a disservice if you don’t get up to Third Place Books, about 25 blocks north of the Seattle border. It’s a book store and a community gathering spot, has live music two nights a week and “Well-known authors to first-time writers present their works at Third Place Books almost 365 days a year!” I don’t work there; I just happen to love it dearly. Check it out:
http://www.thirdplacebooks.com/NASApp/store/IndexJsp