Popular Library was a New York paperback book company established in 1942 by Leo Margulies and Ned Pines, who at the time were major pulp magazine and newspaper publishers. The company's logo of a pine tree was a tribute to Pines, and another Popular Library signature visual was a reduced black-and-white copy of the front cover on the title page.
This early Popular Library book (#147) is now a favorite among collectors.
A paperback book is one with a thick paper or paperboard cover, and often held together with glue rather than stitches or staples. In contrast, hardback (hardcover) books are bound with cardboard covered with cloth, leather, paper, or plastic.
A blank paperback book
Glued binding
1936 Penguin book. Color-coded orange and white for general fiction