On July 30, 1935, Allen Lane changed the world of books. He introduced paperback Penguin Books, bridging the gap between expensive hardcover books and cheap newspapers. With that middle option—and with distribution in places other than bookstores—the Penguin line became a staple of booksellers worldwide. Penguin paperbacks were actually inexpensive enough to be sold from a vending machine.

Another early part of Lane's vision was simple color coding for Penguin titles. Orange denoted fiction, dark blue for biography, and green for crime (this set was quickly expanded to include red, pink/cerise, purple, gray, and yellow). This color scheme lasted for decades, and is still obvious in used book shops. In Lane's first set of books, he published titles by Agatha Christie and Ernest Hemingway, and sold them for the price of a pack of cigarettes. Just ten months after their launch, more than a million Penguins books had been printed.

81 years on, Penguin Books are still being printed (and sold electronically). For a bit more on their history, check out this exploration of Penguin history—and fun facts about their logo, hiding in plain sight. Enjoy:

And if you really can't get enough Penguin history, check out The Bird You Have Throughout Your Life, a multi-part documentary available on YouTube.