lithub.com/on-the-post-war-rise-of-20th-century-british-bookselling On the Post-War Rise of 20th-Century British Bookselling
Victor Gollancz's Left Book Club grew from 20,000 members in its first year to 39,000 by March 1937, and it did so without fighting booksellers. He paid them a fee to receive members' books and put no obligation on them to stock his radical titles, which might have shocked conservative customers.
— via Literary Hub, Andrew Pettegree