Which classic children's book series experienced a dramatic sales revival after its publisher implemented an innovative 'house identity' marketing campaign in the early 2000s?

In the competitive world of publishing and bookselling, even established literary brands can falter. However, some publishing houses have mastered the art of brand revival through innovative product strategies. This trivia tests your knowledge about one of the most successful literary brand turnarounds in recent history - a case study now taught in marketing programs worldwide.

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Harry Potter series (with unified cover designs and 'Hogwarts house' marketing)
Nancy Drew mysteries (with modernized character and interactive online mysteries)
The Chronicles of Narnia (with house-specific editions and digital integration)
A Series of Unfortunate Events (with collector's editions and cryptic marketing)