Quinto sells second-hand books. I spend a lot of time here and have found some inspiring books over the years, both at Quinto and the other shops on this road. Koenig Books on the corner is good for art books, too.
This is a great, free and lesser known spot in London. A glass lift takes you up the side of st.Paul's cathedral right out onto the roof terrace of this shopping centre. A great view over London.