Daunt Books is one of the finest bookshops in London — the original branch on Marylebone High Street occupies a beautiful Edwardian building with oak galleries, skylights, and long oak tables arranged around a central well. The shop organises books by country, so travel writing, fiction, poetry, and history from each nation sit together on the same shelf.
The selection is excellent and the staff know what they're talking about. Other branches exist in Belsize Park, Holland Park, Hampstead, and Cheapside, but the Marylebone original is the one to visit. Worth a detour even if you only come to look at the building.