Fiction (Adult): Make sure I had my sword close at hand as I would be wandering the dangerous lands of Tolkien's Middle Earth, hoping an elf or dwarf or even a hobbit found me before any marauding uruk-hai.
Fiction (Juvenile): One of my favorite books from my youth was Professor Diggins' Dragons by Felice Holman. If I found myself there in the company of the inimitable Professor and his summer charges, children who, before their magical summer of exploration saw little use in school, I would make sure I had my imagination ready for an extensive workout. For wonder and interest is all around, they are dragons after all!
I was going to add a nonfiction entry (my tastes run toward military history) but there are a lot of good books in different periods all of which would be similar - I would try to get myself to headquarters and make myself useful in the staff.
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