Which marketing strategy is credited with helping the 'Harry Potter' series achieve unprecedented global success by creating a sense of exclusivity and community?

The publishing world has seen some revolutionary marketing campaigns that transformed books into cultural phenomena. From midnight release parties to viral social media campaigns, marketing strategies in the literary world have evolved dramatically over the years. Test your knowledge of the innovative marketing techniques that helped certain books break sales records and capture worldwide attention.

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Midnight release parties that turned book launches into celebratory events
Limited edition covers that changed color when touched
Publishing each chapter serially in newspapers before book release
Releasing companion mobile apps simultaneously with each book