Bookshops I Like: Judd Books (Bloomsbury, London)
A few minutes walk from King's Cross / St. Pancras, Judd Books offers a wager that you won't leave without at least one book.
Two floors, often busy enough that you're moving out the way of each other every few moments, and mostly non-fiction. At street-level there is a wide selection of what I call "seconds", though I should find the real word one day soon. Essentially, slightly cheaper productions of books published within the last couple of years, new copies, and on offer for around £4 each.
Downstairs is a trove of second-hand goodies, mostly focused on history, politics and philosophy. The humanities are strong at Judd's, with a very appealing collection of second-hand art, music and theatre books meeting you on your way back up the stairs.
There is even a (small, I admit) selection of anarchism-related titles, nestled above a few more shelves on pacifism. Chomsky is everywhere.
If The Guardian made bookshops, with the aesthetic of Private Eye.