Which publishing packaging innovation, introduced in the 1930s, made books more affordable and accessible to the masses through a revolutionary distribution model?

In the publishing world, book covers and packaging are critical marketing tools that can make or break a title's success. Over the years, several innovative packaging concepts have transformed how readers interact with literature. This trivia question explores one of the most significant packaging innovations that revolutionized access to literature for millions of readers in the 20th century.

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

Penguin's color-coded paperback system
Random House's dust jacket with plot synopsis
HarperCollins' leather-bound collector editions
Simon & Schuster's hardcover book club format