Although I (Jan) purchase most of my books as ebooks, I still visit bookshops and buy p-books (paper books) from time to time. My favourite bookshop in London is Waterstones in Piccadilly which is the biggest bookshop in Europe. It has a restaurant on the fifth floor with a great view of London.
Waterstones bookshop in Piccadilly, London W1J 9HD
Over the years of travelling, I also visited many bookshops all over the world and these are my favourites.