Penguin Books Limited is a British publishing house. It was co-founded in 1935 by Allen Lane with his brothers Richard and John, as a line of the publishers The Bodley Head, only becoming a separate company the following year. Penguin revolutionised publishing in the 1930s through its inexpensive paperbacks, sold through Woolworths and other stores for sixpence, bringing high-quality fiction and non-fiction to the mass market. Its success showed that large audiences existed for several books.
https://en.wikipedia.org/wiki/Penguin_Books