I hear stores that buy used books are rather picky about what they take. Generally people just rent a booth at the @Dubai Flea Market to get rid of them, or they donate them to @The Old Library
I usually go to @Alserkal Avenue in Al Quoz. It’s a hip area with an artsy and young vibe. I would recommend you go to A4 Space in Al Serkal Avenue which is beautifully designed for work or just to chill and read. They have a small library and a coffee shop.