When a sickly young girl suddenly becomes obsessed with inventing new things, her family and friends are all puzzled. What has gotten into Myne? they wondered, never dreaming that the answer is not a What but a Who: Urano Motosu, a book-loving apprentice librarian who died in an earthquake in Tokyo who somehow found herself in Mynes body! And since Mynes world is still in a medieval stage, where books can only be owned by the elite, the new Myne intends to do everything she can to bring her beloved books to the masses in the time she has left.