Just finished the story mode at 99%... Got all gold medals, all story book pages, and all treasures. I clocked out at 14:50 according to the activity log. I did spend an hour or two checking out the figurines and listening to the music, but overall I don't see how you can complain about the amount of content you get for the price. And I haven't even touched challenge mode (is that where the final 1% is?).
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Yeah, last 1% is finishing all the challenges. Glad you enjoyed the game.