Which groundbreaking advertising campaign involved placing mysterious symbols in newspapers and public spaces months before the book's release, creating massive speculation and anticipation?

The publishing industry has seen many innovative marketing campaigns that transformed unknown books into cultural phenomena. Behind many bestsellers are brilliant advertising strategies that captured public imagination and drove unprecedented sales. This trivia question explores one of the most influential marketing campaigns in literary history that revolutionized how books are promoted and consumed. Test your knowledge of the intersection between literature and advertising genius!

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The Da Vinci Code's 'Crack the Code' campaign by Dan Brown
Harry Potter's 'Platform 9¾' interactive installations by J.K. Rowling
Fifty Shades of Grey's 'Submit to Pleasure' viral marketing by E.L. James
The Hunger Games' 'District Identity' social media campaign by Suzanne Collins