What unconventional marketing strategy did Bloomsbury Publishing use that significantly contributed to the initial success of 'Harry Potter and the Philosopher's Stone'?

Before Harry Potter became a global phenomenon with movies and theme parks, it was just a children's book facing significant marketing challenges. This trivia explores the innovative marketing strategy that helped propel J.K. Rowling's first Harry Potter book to unexpected success in the publishing industry, transforming it from an initial modest print run to a cultural touchstone. Test your knowledge about this pivotal literary marketing campaign that changed publishing history!

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They created two distinct cover designs - one for children and one for adults - allowing older readers to enjoy the book without embarrassment
They distributed free copies to 1,000 school libraries before the official release, creating word-of-mouth demand among children
They launched an interactive website where readers could be sorted into Hogwarts houses, years before such online marketing was common
They deliberately limited the first print run to only 500 copies to create artificial scarcity and collector interest