While the master_categories_id is a categories_id, the Categories that hold subcategories are never master_categories_id as only a Category with Products can be a master_categories_id ...
So let's step through this slowly and pretend I know nothing about your Categories and Products as if it were your store and not mine ...
You want to add a Product, what is its products_id? to a Category, what is the categories_id? what is its master_categories_id? and you want it do use the default shipping, what is the default shipping?
Currently, I am aware that you have the CategoriesItem2.zip that I made for you to manage Books, Prints and Prostcards ...
For this new Product that you say is a Book with different shipping, what makes it different? We might be able to identify it by its products_id and adjust the shipping charges based on that, but you need to provide more detail and take baby steps in doing so as I do not know your shop and your shipping like you do ...
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