Favorite bookstores in DC area?

Hello! I like in Alexandria (fairly recently moved out here, less than a year) and have a friend visiting me soon. She wants to explore DC for a day but not with the usual monuments / museums and she had the idea of touring bookstores in the area! We plan on taking the metro in so our main transportation will be walking / metro. What are some of your favorite bookstores that would be accessible from a metro station? (We are both young and healthy so provided it isn’t insanely cold we can walk a ways if need be). Thank you!!