You've got to check out Oh Hello Again on 15th Ave on Capitol Hill. It's the cutest little hole in the wall bookstore that just opened up and the owner organizes it by theme so it's really fun to browse and discover something new.
Elliott Bay! We used to linger there for hours pre-covid. Unrivaled selection, helpful staff, and the Oddfellows Cafe is a fun place to hang out. With lockdown we've been trying to order our books from them too. Terrible website, unfortunately.
I second 3rd Place Books. We go to the one in Ravenna or Lake Forest Park. They have a combo of new and used books. They also buy books. The staff is extremely knowledgeable and helpful if you are looking for suggestions. They also will special order anything you need. If they don't have something in one store, they do several transfers weekly from their other stores. They also have really cute curated gifts. It is a local business very much worth supporting!