Hollie Belton, a creative at London ad agency Leo Burnett, calls for all who use the London Underground daily and enjoy reading, to share their own paperback books with other passengers as part of the Books on the Underground not-for-profit initiative. Hollie came up with an idea to establish a virtual Tube library last year—she designed special round stickers, brought in some of her books and started raiding charity shops.

“The idea is to take an incredible book you want to share with the world, sticker it up, and leave it on the tube, where it can be taken, read, shared, and most importantly, enjoyed. Think of us as your local library, but without the late fees. Just be sure to put them back when you’ve finished.”

Now the movement has gained momentum as volunteers, who share the passion for reading and spend hours in the Underground, join in. Hollie Belton continues to design and print out the stickers herself.

On the Tumblr blog, you can request a sticker and read more about the movement, or join it on Twitter @BooksUndergrnd and Facebook.